Generally I agree - although if ice type coverage isn't something that gets spammed currently, it probably will be if grass/dragon CAP5 becomes as centralizing of a metagame force as it needs to be to make a whole playstyle popular again.
Anyway I think your proposal and mine - Grass/Water - are essentially pretty similar. And although I did point out the fire type counter thing, grass/water is even less apt to be countered by fire types, so I'm really of in agreement on that too. A sunmon that's neutral to fire is still going to take a huge hit from a fire attack, particularly if it comes off STAB from one of the fire types we're hoping to raise into the metagame.
In fact, I have to admit I like Grass/Dragon just as much as Grass/Water. I think they're probably equally viable - unless there's some colossal flaw with my proposal that I haven't considered of course.
It's made with bits of real panther, so you know it's good.