Tropius is incredibly slow, so if you don't run Chlorophyll (and Sunny Day) you risk getting screwed over by anyone faster carrying an ice attack, but this can be fixed with paralysis support and just switching into pokemon that really don't threaten you. Ofcourse, a Tropius evolution could get really bulky, and as such his speed wouldn't be such a serious issue, idk. I wouldn't imagine them making him much faster as it is anyways, he's probably better off slow. Dragon/Grass would have a 4x resistance to Water, Grass, Electric and a resist to Ground. That's some pretty fantastic typing. On the flip side though, it would also have three weaknesses, a 4x ice weakness, a bug weakness and a flying weakness (but no one really caries flying attacks anymore). I really would like to see a Grass/Dragon, but a more defensive one. Imo, we don't have enough purely defensive Dragon Types. Altaria and Dragonite would probably be brought up, but I view these guys as more of a balanced type thing. Hm, I guess they are defensive (in contrast to things like Salamence), but I would like to see a really interesting typing behind it.