Agreed. If you want to experiment with mecanum wheels, you should try them in the offseason. Especially if you are a rookie team. I would suggest making a small drivable base with 4 mecanum wheels, and a simple electronics board. From there, you can practice as much as you want throughout the off season. You can also experiment with different types of weights and attachments, and see how you go from there.

One thing on my team: We almost never try something new that could radically change the robot in the build season. ALWAYS in the offseason.