I just want to clear up: i wasn't agreeing with this being not feature worthy, it is. I just think the integrity of the original could have been kept more intact in the final product.
also:
More true to the style? What style? I wasn't going for any style in the first place.
and:
The design is Metal Slug inspired.
Yes, i know that design != style, but the original had a lot of interest.
Somewhere along the way you changed your mind, i think. If you are happy with the blocky style, then by all means, go right ahead, nothing stopping you. I just feel that somewhere the edits influenced the choice too much. Either way, it's not up to me, or anyone else but you, for that matter.
So anyway, I would continue working on it, i don't think you should call it finished (although it is very good!). for an artist, calling something finished is limiting your skill! you're convincing yourself that you have given it all that you are capable of. Well, opacus, from your beginnings you have come a long way,
keep on going.I'd look up some of the metal slug animations and study the animation on the subpixel level, and then apply it to your tank. And as said before (forget the poster, but i am in a hurry) you could exagerate the movement as well. For example having the hatch flop open as the tank is chugging along, making it look more fluid. Small things like that add a lot of character to the piece. Also, try to get more movement into the tank in the shooting animation, have the tank fly up onto it's back treads when it fires so it looks more forceful, anything like that.
It's very good work.