For example it was a triple/rotation battle only game, what would he have instead of his starter?

I think the most likely answers would be:
> Male Nidoran line
Because the Legend of Thunder
> Houndour/Houndoom
Matches his aesthetic. Starter type. Drawn with Houndoom on Gamefreak's old webstie
> Larvitar line
Has Mega T-Tar in Master's. No one else uses it. Strong and scary looking.

I can also see maybe him having a slight overhauled team with Tentacruel, Octillery, Umbreon or another random choice.