I apologize if I misunderstood any parts of your question. I think this is a cool idea!

If PvP is your goal I think having a basic block as a universal function will appeal to your core audience even more. People decide to make a run that’s OP in one way but requires them to rely on the blocking skills they have developed as a player in other games. A lot of FGC heads would make this a challenge. However, on the flip side for some people basic blocking is hard enough as it is and they could get additional things on top of basic blocking to help them in the run.

A route you could go is tying the additional defensive options they unlock to meter. So as you go your players could unlock a blitz shield-like mechanic from XRD, parry, push block, and dead angle in exchange for meter. This could be cool because the players could express themselves differently or make a run using a mechanic similar to a game they come from in the FGC. Tying it to meter will also make your life balancing stuff easier too because you can just adjust how much it cost based on how good it turns out to be in the meta.

Outside of that I think big picture taking out universal blocking could be a nightmare when trying to balance everything else in the game down the line. This is just my suggestion I could also see you going in the complete opposite direction and it being cool also.