Well....if you disable ACX it can't load converted AC textures from the cache it creates, so technically they "revert" to their defaults. And no, I haven't run any AC textures through Convimx. To my knowledge the AC that need it might be older FS9 stuff. (It might be a thing to experiment on with Convimx.) That's one place where ACX might be the ticket. I can only speak about the AC that I use, which is mostly good old FSX default, the Aerosoft Beaver, and the Carenado C185F series. Everything seems to work fine with them. What AC didn't work in DX10 before running through ACX, and if I get a chance, I could mess with them if they're freeware and I can download them.
What you could do is keep your older AC checked in your ACX setup, uncheck any scenery, delete the old cache and build a new one. I think you'd have to experiment here.
BTW, you just made the fastest photo change in the world from some old guy to an off roader in a flash! LOL!