[EricH]

Actually... Switching drivetrains is something you could get away with, IF you've planned correctly. For example, if you've got the extra hole(s) drilled already, it'd be relatively simple to go from 8WD to 6WD, or vice versa, or 4WD to 6WD, or 4WD to mecanum (with a pair of transmissions added). Planning correctly means that you built the robot to be able to switch--though it does not necessarily mean modularity.

330 did that back in 2005--the competition robot had an extra set of transmission slots so we could swap to mecanum from 6WD if we thought it was a good idea. The testbed--a Kitbot--ran mecanum. We didn't have the weight that year to switch. To this day, 330 has yet to run mecanum on a competition robot.