Alright... so now you can potentially study 15% faster on L5. Something that piles up the sooner in the game you acquire it.
Which means that... Once more a Credo is meta-game defining for the more hardcore/fighters/etc.
It also means that they will want to spend as much time as possible in L5 caves, basically killing (even more) any surface activity or interactions as it will feel like time wasted.
I dunno, those are all things that only become so deterministic because of the lack of some sort of stat caps or - at least - PVP combat stats caps. With some sort of limitation, these would be important but not SO important as the end point would be the same, so you could have variations on the means.
But it is the never ending possibility of stat increasing that makes it so important to always keep ahead and henceforth making certain credos (which were made to add variability and different "ways" to the game) actually become obligations and the new "thing you MUST do".
Anyway, just a few random thoughts, not really "Ideas", just "Critique".
Other than that, keep up the good work :3