This thread is intended as detailed suggestions for future Rubicon tank kits. I'm taking the Rubicon Crusader kit as the template, as it includes 2 turrets as well as the parts for a major variant (the Crusader AA). Not only is it one of Rubicon's most accurate and well engineered kits, it's also very flexible. The idea is to come up with more kits along these lines.
First, the M3 Lee. Not a great tank, or even one of my favourites, but potentially a good subject for a Rubicon multi-option kit.
The basic Lee only served with the US Army for a short period - it had been replaced by the Sherman by the invasion of Sicily. The only options needed for the basic Lee would be different 75mm barrels. The Lee was also used (unmodified) by the Red Army, so that means more marking options (red stars and slogans, mostly).
It would be mandatory to include the parts for the British Grant, including the turret and sand shields (as well as some typical desert stowage). This would be a great companion piece to the Rubicon Crusader. Grants were also used by Australia, which means even more marking options.
The British used the Lee in Burma, and these vehicles were quite distinctive. The kit could include some extra parts to represent the modifications made for service in Burma - smoke dischargers, extra track armour, revised stowage boxes and a low-profile cupola (although the Grant cupola would probably do).
What would really give the kit some versatility would be if it could also build the M31 Tank Recovery Vehicle. That would mean a crane (which was substantial, and would take up a lot of sprue space), large stowage boxes, dummy 75mm gun mount and other recovery-related fittings. It might be a stretch in terms of the parts count, but it was the main US tank recovery vehicle throughout the war and would be a good addition to the existing US armour range.