I would be willing to have an aluminum tsuba if that was the only option offered. I wouldn't paint it, though. I'd use a chemical to force a gold patina on it and seal that in with wax or something (like EDT-220 found
here). But to be honest, I think I'd still rather have a real brass tsuba, resulting slight imbalance notwithstanding.
Whether the lion's head is cleaned up or not isn't a dealbreaker. Pin option isn't a dealbreaker, and I agree that a somewhat idealized offering should really have a brass pin instead of a screw.
I would definitely want a real habaki and seppa, though, as a real sword from the period would have had.
Bottom line: If it were as functional and historically accurate as practically possible (though perhaps not able to be disassembled), with that wonderful molded-from original H1 tsuka, you're getting into grail territory for many, so I hope you can find a way forward. Maybe do a run of idealized first, and then swing back around to doing a screen-accurate-materials version later?