Assuming the driveline that's on is working - why go SS?

If you're worried about theft, that's just money and work sunk into it for little to no payout.

Plenty of people who'd see an SS bike as more attractive than a geared bike, so no advantage there. Selling the gear bits off probably won't bring much money either.

Ny advice would be to ride as-is, until you wear the current drivetrain out - then (maybe) go for the conversion.