I think it should be perfectly possible to format a
tape without those
sensors. Starting from the physical BOT, just make sure you write a
sufficient amount of BOT marks before writing the actual records, and
after the last record, write EOT marks until the physical EOT. The
motor current sense should be able to detect the physical EOT. If not,
I'm OK with manually sending a command to the drive when it hits EOT. I
don't think the motor has enough torque to damage the cartridge,
although I'll test that with a scratch cartridge first.
In most, if not all, such cartridges, the tape is not fixed to the spools
(I've not dismantled a TU58 tape to check, I have repaired several other
cartridges though). If you wind too far, the tape comes off the spool and
you have to dismantle the cartridge to rethread it.
So if you want to go from BOT to EOT, you have to have some kind of
optical sensort.
-tony