Looks pretty solid. Honestly, I would definitely suggest putting the cams on there. Not because belt stretches, but because it acts as great insurance to keep the VersaBlocks in their place, and it's really easy to do.
I'd also size down to 24 tooth pulleys, because then you can fit a 1/4" plywood bellypan underneath your bot and not have to worry about the belt touching the wood.
Also, I noticed you used some other website to calculate center to center distances. That's cool and all, but
WCP has a calculator on their website which is also extremely useful.
Other than that, it's really solid as long as you make the changes you said you're planning. I'd personally do the math on your 3 CIM transmission using
JVN's Mechanical Design Calculator and the attached Acceleration Calculator (sorry, forgot who made it) to see if you really need the extra CIMs on each side. I love 6 CIM drivetrains, but you can see in the math they're only marginably better than what you'd get from a 4 CIM shifter in most scenarios unless you're running PTO. I plan on running WCP 2 CIM DS this season even though we ran 3 CIM in the offseason because it's pretty much the same (unless you really care about .16 seconds of travel time).