I had planned to fuse around 25 Illuvials this weekend, that I collected and level up for quite a long time, and they are all ready to be fused. (some to try to get good stats, some to make skins, and got 3 T5 I am missing to complete the full set.) so I can fully relate to the depressing felling when finding out fusing them will be much more expensive now, and I am "kicking myself" for not fusing them a lot sooner...
Regarding the skins and BP already minted... This will obviously be the most difficult part in changing the current system. But I think converting existing Skins to the new type, that doesn't require a specify suit type, will be the most fair solution... this means that if you have a "AeroWeave Sear skin" and a "Cybercore Sear skin", they would be converted into 2x Sear armor skin, and you would be able to use that skin for anywhere in the games regardless of armor/suit type, and you could then sell one of them.
It might be a bit more tricky with the Blueprints, as they would not necessarily exist as NFT's with this new system, and they do represent a value both in terms of the material and time it has taken to produce them on ILZ. I have also minted 16 drone blueprints myself (mostly focused on getting "Hilde drone skins", and was planning to make skins out of some of them when I had fused those that I was missing). But I don't really see any fair way to compensate for the already minted BP other than convert them into Fuel. Maybe someone can come up with something better.
I think collecting all the pieces and "forging" the skin inside ILZ could actually be quite good, especially with some UI improvements to how we organize and see the BP/Skins in ILZ. 🙂