It reminds me a lot of the tanks from the Advance Wars nintendo game. I think that if you shrunk the design's width by a few studs and moved the turret forward, you might like how it looks more. I'd personally try moving the cockpit into the turret, although I know having the space is a problem. Adding some color to the design would help too, a military insignia, or a ring of color around the barrel maybe. I'd try some simple details and greebz like a few 1x2 grill tiles near the engine section if you felt like it. Good work.