If you decide to design your own, do not forget the skip speeds or the darn thing will shake apart.

What is skip speeds?
do you mean soft start?
No, ANY inverter worth its salt can be programmed with speed ranges it will not stay at. If the motor is accelerating, it will, of course, pass through those ranges but if you select a speed in the deadband it will be replaced with the closest speed (for some inverters you can select upper/lower replace) outside the illegal range. The reason is that any piece of heavy machinery has some resonances and if you run at the resonance frequency, the darn thang will eventually shake apart.

Erik