I think it's a good idea. Crafting itself has kind have been lame lately with all the new stuffs coming from Synergy. And it's a hassle trying to find other people who have the right crafts every time I want to do Synergy. (It's hard enough to find other people who have synergy leveled to make some of the harder items!) I don't think allowing each character to have two crafts @ 100 will cause many problems, since a lot of us have alternate characters that have crafts at 100. (I personally have goldsmithing and leather on top of Kirschy's Alchemy.)

The only major change I can see, is that certain items will change their HQ tiers... but with items like Dusk Gloves+1 already being T1 due to crafting changes, I can't see this being a problem.