Same! Would love to see more of Chompers parents. And I haven't watched the TV series but I still think the question of his future in the The Valley is completely unresolved.
You actually have a pretty good point, focus on the other main characters, and you’ll create a good movie (just like the 8th movie).
I think any storyline involving Chomper is going to have a lot of built-in-potential for emotion and conflict. On one hand, Littlefoot practically adopted Chomper and out of the entire gang seemed the most keen to care of him and to think of him as family.
On the other hand, Littlefoot also lost his mother to a Sharp Tooth, and there's gotta be some left over trauma there that I could imagine would make it harder for Littlefoot to deal with the fact that one of his best friends is actually an apex predator. It might make him uncomfortable level, although undoubtly he wouldn't want to show it, or even more likely, he might go into full on denial mode and refuse to reckon with it altogether.
Anyway, there is A LOT of potential there plotwise for a new sequel.