With over 800 crafting levels under my belt, I think I'm qualified to give an honest opinion on the subject.

I personally don't think raising the crafting caps will make much difference at all. As one or two people mentioned, there will probably be increased demand for some items temporarily for capped crafters to reach their new crafts. This would annoy me, but I assume the effect won't be that bad and won't be too long term. (Crystals on the other hand may get completely out of hand. More on this below.) Also some items will be able to reach new HQ tiers, but there are currently only a handful of these and none that are currently worthwhile.

The change has a whiff of populism and desperation to me while failing to fix the true problems as I see them. Here are changes I'd much prefer to see:

1. Get rid of material losses for synths where I'm above the cap. These are just incredibly frustrating. I think this is why breaks were (thankfully) completely removed from Synergy. (I understand that part of the game is luck, but bad luck is a lot more frustrating than a lack of good luck.)
2. Give HQ results for more crafts. What I mean by this is that there are a lot of low level crafts like Sheep Leather or Cotton Cloths where you get HQ animations, but don't get any extra materials. These always seemed like a slap to the face especially when followed by a critical break of a synth where I'm 100+ over the cap. I think adding some extra HQs might give high level crafters an incentive to keep the materials on the AH stocked. Conversely, it could hurt the profits on NQ synths so it may not be win/win all around.
3. Show me the crystals! The other day I sat down with a nice cup of tea to do some synthing, but I found out there wasn't a single earth crystal available on an auction house anywhere on my server so I was out of luck. Crystal prices today are even higher than they were in the midst of the great inflation period. This change would only put more pressure on the already minuscule supply.
4. Show me the synths! I can't think of a single worthwhile non-Synergy synthesis that has been added since Abyssea was released.
5. Fix synergy. I love the concept of synergy-- team up to accomplish greater synths. The problem is that the menu-based design is miserable, and also seems to be unfair. Since the system is server based instead of client based, I've heard that some people can thwack four or five times before an overload, but I've never been able to get off more than two or three. That's unfair, and incredibly frustrating! The proposed change seems to be an admission of the failure of utilizing teamwork for synthesis by making everything soloable. I'd much rather the design be fixed than completely giving up on the teamwork aspect.

In summary, I am intrigued by this change and agree that it could bring some benefits, but I hope you will consider some of my suggestions instead. Thanks for your time.