I wasn't aware of the amount of overhead when using more/less contol files. Probably it's neglectable...

Sure. However, I would put one copy of the control file on another disk even if it is local to the box.
The SAN has no local disks. I can ask the 'network service desk' if it is safe/possible to use a local disk of a server. (The server is in a cluster and maybe this is a problem?)