Dore.
Put it on the MML so that services from Chesterfield/ Dronfield etc can call there too (at the moment, Dore station is on the single track chord between the MML and the Hope Valley line, which limits the number of services that can use its single platform and limits the time that they can dwell there, given that its on the bottleneck chord).
Maybe even move it further north, towards Millhouses?
Rotherham Central.
Replace it with Masborough. Central Rotherham is a ghost town nowadays (the usual problem of being located between a big retail park - Parkgate - and a big mall - Meadowhall). Diverting services over the flat junction at each end and negotiating the single track Holmes Chord is a major disruptor that causes delays. Much better to have a four track station at Masborough instead - run a TramTrain shuttle from there through central Rotherham to Parkgate if you must.