Clutch start safety switch?

Don't use it. Just wire the starting relay directly to a ground.
Pushing down the clutch pedal during start-up puts a lot of force on the axial crank bearing, and when there's no oil pressure during the start-up, those bearings might not like that very much.
Plus, the countershaft is rotating during that start up, and starts slinging oil everywhere, which makes it easier and better to engage first gear.

Toon