[Nuttyman54]

Team 190 had a swerve drive in 2009, and had the option for a setup which was primarily tank steering, but switched to swerve mode when the trigger on the joystick was held down. We also used the 3 axis joystick for swerve functionality and it worked well. It can take some practice to get used when to switching back and forth (and remembering to do so), but it might be more natural for your driver if he's used to tank drive. You might do best to change the front wheels to omnis for this setup, so that it will turn better.

You should still be able to swerve with this setup, although the system might not react the same way as it has been. Omnis would still provide the necessary force in the necessary direction (CoF shouldn't affect it unless they have too little weight on them). You might see a difference in rapid direction changes, as the omni characteristic could cause the drivebase to fishtail or otherwise swing in weird/unexpected ways, but it's hard to say for sure. It's also prudent to note that omnis do have some vibration associated with them, and while this might not be an issue, it could also cause problems in the swerve system if the vibration is severe.

If your robot turns ok tank style without the omnis, this will likely give you a more predictable system, but chances are that four traction wheels will not be happy turning like a tank drive.

If it is a fairly simple process to switch the current traction wheels for omnis, I would recommend you prepare that for the regional, and give your driver the option for tank and swerve. He might need some reminders of when to use the swerve functionality to his advantage, but working to add that in will probably produce better results than having him struggle with the current system, if he's used to tank.

$0.02