Basically, I want to make something akin to picrelated with the player HP/MP being displayed at the bottom of the battle screen rather than on top. Any way to do that?
Another nice thing would be to disable the bars and make it just numbers, but that's besides the point.
Yet. Full customisation is definitely on the todo list, and a high priority too, but I myself wasn't expecting to get to it very soon since there are many other high-priority things.
You can disable the bars, there are Battle System Preference bits for that: Show health meter, Show MP meter, Show ready meter. (But if you disable the ready meter then there's no textual replacement for it.