>>10405608Imo, the origin c6 zakus are the best zaku to army build, a few variations can be made with 2 or 3 kits. Parts are pretty interchangeable as well. Revive zaku is ok but not as customizable put of the box.
For GM I would say ground GM because its got a good weapon variety and the better GM option currently. The old HG GM is cheap and an easy build so there is that option as well. Unless you want master grades. It will get repetitive fast building the same kit 2 or more times in a row ao there is that to think about.
As for dioramas, what size are you talking about? Most you will see are diorama bases. Few have a larger layout due to space and time etc.