I had zero issues with difficulty. You're given type advantages in the immediate area, it's rather easy to level up enough and you're given a good moveset. Any complaints about difficulty are likely from people who mindlessly attack, attack, attack.
Even without utilizing type advantages, if you utilize the stat effect moves, then your starter is more than enough. Not to mention it gets OP if anything as it levels up.
I say keep the difficulty curve, add more battles and what not. I'm more curious what your outline plan is (not time related).
Will you focus primarily on adding towns, gyms and mons (with a scene tossed in) to start and then fill the world out with H-content? Or will you try a balanced approach? Do you have plans for more original mons like Adalass (can I fill my team with 6 sexy mons)? Will there be 8 Gyms, Elite Four and a Team Rocket?
My own personal recommendation: After adding in the base content (town, gyms, mons and Elite Four), then add in post-battle content, vs seeker stuff. By that I mean, after battling a Lass, Picknicker or bipedal mon in the wild, then give the option for H-scenes or move on. It'd be a good way to encourage replaying.