Someone might ask why a game would even need a magical item creation system in the first place when the list of failures of previous systems piled to the heavens and we have two perfectly good alternatives for acquisition: namely rolling for treasure and just purchasing it off of a list. So why have a system at all?
1) It increases ownership of your item and thus peoples' attachment to it. Let's face it, players are always going to enjoy the airship or the fortress base or the infinity plus one sword more if they assembled it from component parts in a catalog rather than just purchasing/finding the already-intact good.
And that's pretty much the only advantage to it. But it's a really powerful one. If you've ever listened to someone talk about how much detail they've put into their custom praetorian guard or their tricked-out autocrossbow, you know much it makes genitals tingle. And I think that it's enough of a reason. However, there are some problems to it:
1) Certain types of created magical items tend to be really bland--no one is ever going to intentionally assemble an Immovable Rod or a Decanter of Endless Water. People will always go for the most combat bonuses if you give them the chance.
Solution: Limit magical item creation to certain items. Either the item has no direct combat utility in of itself, or it's not expected to do anything interesting beyond a strict combat function. People should only be able to create vehicles, strongholds, weapons, and armor.
Solution 2: Have a random chart for 'miscellaneous special effect' that a player is forced to/can choose to roll on. So your blinged-out armor also has the special effect of making all herbivorous animals in a 100' radius ravenously hungry for flesh.
2) Created magical items have a high chance of overshadowing randomly generated magical items. Let's face it, part of the fun (and risk) of having a randomly generated item is that there are a lot of functions that you aren't going to use directly. This helps keeps them unique. But if you get to choose exactly what you want, it'll just reinforce idioms you already have.
Solution: Randomly generated magical items are pound-for-pound flat-out stronger than created ones. For example, the strongest sword you can create at level 12 is a +5 sword, while you have a good chance of finding a +7 sword out in a random pile. Created ones give you the advantage of specificity, randomly generated ones give you the advantage of raw power.
3) Creating magical items takes up time and slows things down.
Solution 1: the game rules should strongly encourage DMs not to create magical items during game time. That thing needs to be done between sessions unless the DM says otherwise. If a character already has a blueprint, fine, but no working on that stuff at the table.
Solution 2: the magical item creation system is weighted in such a way that there's absolutely no need to combine minor bonuses for a bigger effect. While I'm not saying to get rid of the bonuses, people should not have the choice between picking four minor category bonuses and two medium categories. They can get two mediums, a medium and a minor, or two minors. Yes, it's intentionally made so that most people will want the best available. Deal.
4) 3E's system of determining bonuses down to the point was stupid and required algebra to optimize. While people enjoy looking through catalogs, no one likes doing math to determine the biggest bang for their buck they can get for 20,000 gold pieces.
Solution: The players are not allowed to adjust bonuses directly. They instead select from a list of components which have the bonuses waiting for them already and the amount of components they can select are based on single-digit addition. For example, the Minor Water enhancement automatically comes with water breathing, a swim speed, and the ability to reroll a failed reflex saving throw once per day in addition to whatever item-specific properties it should have (for example, minor water on a vehicle makes it submersible, on a weapon makes it acidic). The character is allowed to craft a sword with up to one medium enchantment and one minor, or two minors.
5) Like the Magical Item Mart, basing a magical item creation system on some real-world resource encourages people to live like hobos and strip down the Mayincaztech temples for a minor boost in power. Unfortunately, you will have to put a limit on it somewhere and somehow if you don't want people carrying a golf bag full of geegaw.
Solution: A chakra system of some type. Just creating and hoarding magical items drains your chakra meter or whatever. If you 'release' a magical item it decays quickly. Of course this operates heavily under the assumption that you don't find created magical items out in the wilderness or in treasure chests. And I'm okay with that.
Solution: Limit magical item creation to certain items. Either the item has no direct combat utility in of itself, or it's not expected to do anything interesting beyond a strict combat function. People should only be able to create vehicles, strongholds, weapons, and armor.
Solution 2: Have a random chart for 'miscellaneous special effect' that a player is forced to/can choose to roll on. So your blinged-out armor also has the special effect of making all herbivorous animals in a 100' radius ravenously hungry for flesh.
2) Created magical items have a high chance of overshadowing randomly generated magical items. Let's face it, part of the fun (and risk) of having a randomly generated item is that there are a lot of functions that you aren't going to use directly. This helps keeps them unique. But if you get to choose exactly what you want, it'll just reinforce idioms you already have.
Solution: Randomly generated magical items are pound-for-pound flat-out stronger than created ones. For example, the strongest sword you can create at level 12 is a +5 sword, while you have a good chance of finding a +7 sword out in a random pile. Created ones give you the advantage of specificity, randomly generated ones give you the advantage of raw power.
3) Creating magical items takes up time and slows things down.
Solution 1: the game rules should strongly encourage DMs not to create magical items during game time. That thing needs to be done between sessions unless the DM says otherwise. If a character already has a blueprint, fine, but no working on that stuff at the table.
Solution 2: the magical item creation system is weighted in such a way that there's absolutely no need to combine minor bonuses for a bigger effect. While I'm not saying to get rid of the bonuses, people should not have the choice between picking four minor category bonuses and two medium categories. They can get two mediums, a medium and a minor, or two minors. Yes, it's intentionally made so that most people will want the best available. Deal.
4) 3E's system of determining bonuses down to the point was stupid and required algebra to optimize. While people enjoy looking through catalogs, no one likes doing math to determine the biggest bang for their buck they can get for 20,000 gold pieces.
Solution: The players are not allowed to adjust bonuses directly. They instead select from a list of components which have the bonuses waiting for them already and the amount of components they can select are based on single-digit addition. For example, the Minor Water enhancement automatically comes with water breathing, a swim speed, and the ability to reroll a failed reflex saving throw once per day in addition to whatever item-specific properties it should have (for example, minor water on a vehicle makes it submersible, on a weapon makes it acidic). The character is allowed to craft a sword with up to one medium enchantment and one minor, or two minors.
5) Like the Magical Item Mart, basing a magical item creation system on some real-world resource encourages people to live like hobos and strip down the Mayincaztech temples for a minor boost in power. Unfortunately, you will have to put a limit on it somewhere and somehow if you don't want people carrying a golf bag full of geegaw.
Solution: A chakra system of some type. Just creating and hoarding magical items drains your chakra meter or whatever. If you 'release' a magical item it decays quickly. Of course this operates heavily under the assumption that you don't find created magical items out in the wilderness or in treasure chests. And I'm okay with that.
So what is my ultimate vision for this system? Something like this:
Bob the 8th-level Paladin uses a combination of all three systems. His go-to weapon is the Holy Avenger Warhammer that the DM rolled for him (RPed as receiving it as a reward from the king for vanquishing a devil), because it's better than anything he could ever create and frees up his chakra for other projects. However, his armor and his backup bow and arrow were created with his own chakra using the magical item creation system. Since cool barding is almost impossible to find, he used his last bit of chakra to make a special armor for his pegasus that gives it two extra mechanical heads (that breath fire and lightning) and after a 1-minute startup allows it to fly at supersonic speeds for 20 minutes a day. His other gear like his helmet and a magical ring he just purchased from the magical item mart.
