[Tom Ore]

1) I think you will see significant wear on the rollers
2) Dirt could get under the rollers, making them sticky and maybe increasing wear
3) We always put down carpet whenever we run on a surface that needs to be protected. We also put down carpet when we demo outside with our competition robots. (We keep an old roll we inherited at our shop.)

If you do you run mecanums, buy a set rather than trying to make them.