I do not mean to rain on anyones parade. But, there is a
potential problem using single pole starter relays in this
circuit.

If the relays with suppression diodes drop out slower than
they pull in, you could have an overlap situation where both
k1 and k2 for instance are closed at the same time.

This could cause a very high current pulse which would blow
the fuse and could weld the contacts on the relays.

This would only happen if someone were to flip the control
switch quickly from cover on to cover off or vice versa
without a pause in the center off position.

The easiest way around this would be to use a switch that
forces you to release pressure on the lever while in the
center off position before it will allow you to proceed to
the other position.

Such switches are made. Unfortunately, I don't remember who
makes them or who sells them.

The timing of the particular relays that you use may not
present this problem. But, it is something to check before
turning the system over to the user.

Ron