I like the idea of locking some modifiers behind some kind of gate, whether it's an upgraded crafting station, hardmode, or just certain boss kills. I dislike the idea of removing the random factor to the modifier creation though. It takes away that ARPG element and takes away the incentive of finding duplicate items. I mean, I might have a decent last prism, but I could potentially get an incredible one.
Furthermore, I think so of the blue modifiers (such as lava-proof as example) should definitely be locked until later game.
For instance, gravitation. This, I feel, should definitely come much later or removed. I realize the effect can be garnered with a potion, but at least potions come in limited quantity and duration early game.
I judge the power of a modification based on how much of the content/features the modifier replaces or makes trivial.
Gravitation does the following:
- Removes the need to traverse dangerous environments, early game, as soon as you get your first (potentially) accessory.
- Give you access to floating island treasure immediately upon acquiring. Such as Star Wrath at the beginning of the game increasing your character power drastically.
- Makes grappling hooks, immediately, obsolete.
- Removes the threat of falling damage with quick activation (Or by providing access to a horse shoe on a floating island)
- Significantly lowers the threat of any monster without a method of attacking a character with a height advantage.
I recalling having thought of some others, but I can't seem to remember what they are at the moment. I think the capability of getting gravitation early game or right at the start of the game is more than should be given. That said, I think mods like well fed, shiny, feather fall, and flipper are all the right power level as they only provide a small advantage rather than major game altering advantages.
I also believe that complete lava-proof is pretty powerful. It makes getting obsidian and hellstone a breeze and completely removes the danger of lava all together. All you have to do early game is dig down to some lava, submerge, and let the mobs kill themselves in the lava and collect the loot. Early inferno is a bit powerful too as it provide a significant amount of constant AoE damage well beyond the capability of a starting character.
Just some things that I'd like you to consider. Currently, I feel that your modification mod is currently the best one available. You have some competition with the revival of even more modifiers, but I think his modifications are drastically underpowered making them a bit negligible in the game play. However, it's quite possible that it will not remain that way.