Aer Arran and Flybe have both run WAT-MAN in the recent past, Im genuinely unsure if LPL-WAT has been served in recent years.
In terms of a based aircraft, I would highly doubt a return of MAN-LCY due to the decent rail services now on offer, and as for MAN-ANR, its been tried by VLM, Cityjet and bmi regional with varying degrees of success, so unsure its worth another go.