keep the design simple. the fewer moving parts that can break the better.
design for serviceability. you shouldn't have to
this to get to a bolt.
pick your driver before the season and design the robot to fit their driving style so you get the most out of your machine. i've seen too many teams with mecanum drive, never really use it. as an ex driver who has a very aggressive "in your face" driving style, a 13fps single speed 4cim robot with average traction was suboptimal for how i drove.