Surprisingly enough, there arent as many people as you think in Hoenn,
and it's awesome to actually be able to enjoy the Hoenn region without so many people crowding it to the point where it lags and you cant see the npc's anymore.
If you have access to Mt.silver (which you should, if you are a Kanto&Jhoto champion) training your rattata to lv100 is relatively easy. Just train on the lv 48 Teddiursa's & Ursarings on the Upper mountain side. Only took me 2 hours in total without any exp boosters.
They have to make it fair for everyone. I hope that information helps.