It seems that the kits of both their V-100 and V-150 armored cars have identical chassis and axles, though the V-150 had the stronger axle types. So does the kit represent the V-150 type, and they just reused it for the V-100 kits, or what's the story?

I'm no expert, but an axle is actually just the shaft that runs internally though the housing from the differential to the wheel, so as long as the housing could take the stronger axle unit the standard housing and diffs may still have been used.

I understand the suspension was a different matter where according to Hunnicutt's History of Armored cars, the leaf springs were modified for the V-150. He does not say how.

This might help you
http://data3.primeportal.net/apc/brent_sauer/v-100_commando/images/v-100_commando_11_of_20.jpg