Two GMFs and one VFD

Over the weekend I got a really good deal I could not refuse on another GMF 1HP 3P grinder and am now looking at putting my small multitool Linisher onto that grinder as well as making it variable speed.

One thing I did not want to do was fork out for yet another VFD
but
its proposed next door neighbor will be this identical grinder


So I thought, why not use the same VFD with a suitable cross over 3P switch between the two grinders.
Now because of the some individuals who occasionally use my workshop I won't feel comfortable unless there is some sort of lock that prevents switching the cross over while the VFD is running a grinder.

I have in the past proposed using a manual cross over switch placed inside a box, the inside of which is only accessible when the output of the VFD is off.
I was thinking of using a simple 12V door door latching solenoid to lock the door, and the lock is activated by a DPDT switch with the other side activating the VFD.
VFD ON - door locked

Maybe there is some sort of 3P switch that does this already but I expect that it will be pretty ex..

Any other suggestions welcomed.