In general wheel slippage issues can be ameliorated by changing the acceleration limits.
I would suggest that you lower the acceleration (and perhaps the jerk) limits in the motor controller.
See the motor controller documentation here:
Most of these parameters can be dynamically set with rqt.
If you would like we can get you motors with different tyres, but this is not recommended, softer tyres will make the odometery less accurate as will tyres with a wider profile. That said though we can investigate options email firstname.lastname@example.org for more information.
Using non-standard brushless hub motors is also not recommended as using the wrong motor can destroy the motor-controller. Our master controller can switch 500W of power for the motors alone - let alone power supplies, computers etc. It has to do this very efficiently or the motor controller will rapidly over-heat. Our motor controller is tuned to the motors we supply and while others may work - there is no guarantee. We have tried non-standard motors which resulted in lots of magic blue smoke.