Modeling a Sherman would give you a lot of bang for your buck. Just think of the varients that could be produced from the basic welded hull Sherman.... there's the 75 and 76mm versions, the Calliope (rockets), the Jumbo (assault tank), the Crocodile (flamethrower), the Firefly (17pdr), the 105mm howitzer equipped Sherman, the HVSS or "easy eight" Sherman, and if you take the turret off and give it an open top you can do vehicles like the Priest. An added plus for doing the cast hull Sherman would be the possibility of modeling a Duplex Drive version.