I really am enjoying it. It is pretty close to a perfect product in terms of what a convenience ROM for this game should be IMO.
I think charging BP is fine, there comes a point when all they're good for anymore is to buy some vitamins, which aren't exactly the most useful thing since the EV training is so easy. Move Tutors would be a fine thing to spend excess BP on. It's just the prices are ludicrous relative to the pace this ROM has everywhere else. Item BP prices are fine though, since you only really need to get them once each. In terms of how it makes sense: they're secretly Scott's employees. You think you're done with his theme park and just want to fight other trainers, but then you really want a swampert with ice punch and rock slide. So you tell yourself: "just this one run of Battle Pyke, and I'll have all the BP I need". And next thing you know, you've spent the last month setting a new record at the Pyramid and Scott's pockets fill up with TV specials, merch with your face on it, and whatever money he gets from people betting whether you'll survive the next round xD.
Oh, there's something else. The gen VI XP share is quite annoying, requiring 6 A presses for a full team with a pause before each A press every time you defeat or catch a mon. Don't get me wrong, it's way faster than turning it off or switch training, but the amount and the awkwardness of the mashing feels kind of bad, particularly for your thumbs after an extended play session. I'm assuming there's not much you can do about that without a major change to it, but there is something else I hope you can change easily: double battle XP gets halved for everyone in the party. That means if I get 2 trainers to fight me at once, I'm cutting in half the XP I get from each of them. Maybe that's balanced, but it just feels bad. Please do try to change this.
Lastly, and I only thought of this because i randomly got it myself during my playthrough, I think you should consider adding an NPC that gives your mons pokérus. Not that I need it any more :P.
PS: I just encountered a glitch, not sure if it's known. The guy who gives Return/Frustration won't talk to me. Maybe it has to do with it being a weekly event?