pic: High Traction Drivetrain Concept

[Cothron Theiss]

Does that 38 lbs include the battery? 38 sounds a little heavy, but that may just be the 8 wheels and the relatively heavy gearboxes and motors. I would suggest you look at JVN's design calculator to figure out your gear ratios. You're designing this drivetrain to win pushing matches, so you'll need to make sure your low gear is low enough that your motors don't burn out.
Also, you may want to push the Colsons on each side out to the front and back of the chassis. Your inner wheels are quite close together, and while the Omni's will cause some turning scrub, you may find this still turns too quickly for your driver's comfort.

If you want to drop your price point on this, you could look at a different (custom?) gearbox. You could also consider switching to smaller wheels for the purpose of using the 3.25" Omni's that already have the hex bore. This will save about $12 per wheel since you don't need VersaHubs. There are other small things here and there you can do to lower the cost without increasing the need for machining much.

Also, I see no reason not to use #25 chain.