Looks cool. I always liked NBA Jam, it had a good pace to it. 3D killed backetball games, the side on, parallaxy view on Jam was ideal, so 2.5D like you have there is what I'd do as well. Best thing is that you'll be able to get a lot of detail if you stick to just 2 or 3 players a side, so a 1000 poly character will look as detailed as you'd need. Lots left over for mirrors, shaders, and particle effects.
Looks like a very interesting project, will keep my eyes on this
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I always thought that if it's not side on, then it has to be first person - third person sports games just annoy me.