One of the most crucial parts to creating a drivetrain is serviceability. You most likely will have problems with your drivetrain because nothing is perfect. Make sure that you can pull off a gearbox or a motor in case something happens.
We had so much power to each wheel last year (1 CIM and 1 Mini CIM per wheel (4 wheel mecanum)) that we ended up wearing the gears in the gearbox so much that only 1 CIM was driving a wheel. It took us a while to replace it (about 1.25 hours). Part of the problem was we didn't use more than the standard andymark grease. (The funny part about this story is that since we had a PID on each wheel, we didn't notice the loss of power until we heard the gearbox grinding)
Also, clever placement of items (in terms of making room for other attachments) can be a big help. We put our compressor inside a section of our frame that would have otherwise been unused.
Don't forget to make some nice, rigid spots to attach end effectors/ game piece manipulators!
And last but not least, try to keep the CG as low as possible. We had 6 CIMs and 4 Mini CIMs all under a foot off the ground. It helped us not tip over, even with a relatively heavy ball throwing mechanism.
I would highly recommend looking
at HOT 67's tech notes, as well as other teams that have their drivetrains figured out. We based ours off 67's and it worked out really well for us.