Yeah, MP cap is a complete non-issue as far as I'm concerned.

MP costs are already percentile based, so the only change really is that Piety won't be increasing your pool and will instead be increasing MP regen.

Of course, this also means that MP restoration skills are being relatively buffed. Since things like Lucid and Refresh (Also Elixirs if that's a thing you use) deal flat amounts of restoration not percentage based.

The only things that are taking a hit, MP restoration wise are percentage based restores, like Aetherflow, Assize and also The Ewer (Since cards are being reworked...) - That is, unless they are being adjusted and/or considered with the change.

I think this is one of those things that Yoshi was on about when he said "He didn't want to leak any of the changes early, because some of the changes might not make sense without seeing the complete picture"

MP standardization should simply mean that MP restoration effects are easier to balance, since everyone will get the same benefit from everything. As opposed to things like healers getting less out of Refresh/Lucid because of their larger MP pools than the Mages that don't have Piety as a stat to bolster their MP.