Mate, you really are better off asking this on the BKC/CWC/FWC forum of the owner, lots of people ask the same qeustion (and in the end it boils down to taste, so you will see a ton of answers).
I can tell you that back when I did it, I made sure I did not have the amount of diversity you have. Standarddizing helps and in 1/600th scale yopu are going to show units, not singles. IIRC, going on memory here, 30x30 for infantry and all vehicles, FAO and FAC on small circle (maybe 20mm) HQ on 30mm circle and CO on 40mm circle. Aircrafts base don't matter. I think you could play Spearhead with this as well.
Actually, for my old group, size of the base didn't matter cause you shot from the end of the shooters base to the middle of the targets base. That way you never had discussion about base size and we all could do what we thought looked best.
Your 0.8 ply with magnet basing will end up being 1.5 thick anyway, we never thoughts the bases stuck out. No need to go "thin as possible" as for recognition purposes adding a small tab to the tab helps immensely with the recognition of your units in this scale, but to each his own.