Wow - this kit is really shaping up…
I really like the M3 with pedestal-mounted .30 cal. I think the .30 cal should have the earlier curved cradle, but that probably doesn't matter.
The M3A1 looks great too. Is that radio installation right though? I thought the radio set went behind the middle front seat, and was smaller, but I'm not sure. I also thought it was the box-like BC-620 set that was fitted. The only photo I could find of an M3A interior is below, and it's not very clear.
I've just noticed that your canvas hood overhangs the windscreen. This isn't correct - it should be flush with the top of the windscreen.
The rear stowage racks on your "M3A2" were retro-fitted to the M3 and M3A1 in September 1943. I've seen a couple of photos of halftracks in service fitted with the ladder-like side racks, but they seem to have been rare. I think the "M3A2" version of the .50 cal pulpit might be based on an inaccurate kit, like the Tamiya one.
The M4 Mortar Carrier was built on the M2 half track, not the M3. The mortar carrier version of the M3 was the M21, which had a forward-facing mortar and a different internal arrangement to the M4. It would be great if you could include the M21 version in the kit, but I guess that's quite a lot of extra parts.