Originally Posted by Cieyrin
I like how a lot of these function, though I have issue with the Expertise crystals, given you can't use the Greater crystals unless your exotic weapon is already +3 and not every bec de corbin out there that you want to use is going to be a +3 whatever one.
I know what you're trying to go for here with the different tiers of equipment but I think I'd move to make them just one crystal of least power so that any weapon or armor you care to plug it into only needs to be masterwork to use properly. Still not exactly perfect but more on a parallel with the Skillful weapon special ability and all around more user friendly.
In agreement about the expertise crystals. Basically, you have to wait for a +3 weapon to use any exotic weapon, but apparently you can't apply that expertise with lower weapons.
I'd go a different path: the least crystal grants expertise when wielding the weapon (so you can change it from a rapier to a spiked chain to a maul to a Jovar greatsword to a minotaur greathammer to a ribbon rapier) and keep the property. Same for armor; though that would mean you could go anywhere from chain shirt to full plate in a matter of minutes, but since most of the light-armor classes already have abilities that depend on little armor, that means it would be more of a novelty than anything else.
I'd suggest a crystal of Finesse, upon which you can treat any one-handed martial weapon as a finessable weapon (but not two-handed weapons) for purposes of Weapon Finesse. That could open the Weapon Finesse feat for even more weapons (mostly longsword and scimitar which are the most evocative) than normal, but you would be essentially locking out other augment crystals (since you can only apply one augment crystal per weapon or armor).
I'd also suggest a Least, Lesser and Greater Crystal of Armor Adjustment. The lesser would decrease the armor check penalty of an item by 1 and increase the max Dex bonus of an armor by 1, the Lesser would be 2 instead of 1, and the Greater would be 3 instead of 1. Though, I'd personally go for -1 ACP/+1 Dex for Least, +3 ACP/+2 Dex for Lesser, and +5 ACP/+3 Dex for Greater. That way, you could make heavy armor and Dex-based characters an applicable option. I'd also add to the Lesser Crystal of Armor Adjustment that the armor does not restrict your movement (if medium or heavy armor) thus you can move at your base land speed and use skills like Tumble on said armor, and the Greater Crystal of Armor Adjustment would allow you to treat the armor as lighter for purposes of class-related abilities (heavy to medium, medium to light, light remains the same).