First, I think it's important to say that I'm loving this hack so far.
The first gym sucked all the fun out, however. The combination of Metronome, Cute Charm and ESPECIALLY that Jigglypuff's Sing meant that my victory seems more up to RNGesus than anything I could personally do. Sometimes I'd come closer, sometimes I was further, all while steadily levelling up from retrying the gym over and over again.
That Jigglypuff would easily take all the hard work I had to do to get to it and throw it away, putting my entire team to sleep, so all I could do is watch, and hope that one of them woke up at some point so I could put at small dent in its HP bar before it put it to sleep again.
I also don't remember ever encountering any Poison or Steel-types along the way. Did I miss Nidoran somewhere?
EDIT: Actually, there WAS Zubat, but I don't remember it ever learning any good Poison moves before it evolves... come to think, does it learn anything good before it evolves?
My team consisted of a full 5 at that point, plus an HM slave for later, though, so perhaps my experience is being spread too thin? I don't think you should have to grind for the first gym, even if the difficulty is supposed to be higher.