A segregated Metrolink route could run (separate from the railway) from Piccadilly Metrolink station to just beyond Ashburys, then via Reddish North and Romiley to Rose Hill. For the 1.5 miles (approximately) between Romiley and Marple Bridge Junction, the route could be shared with Network Rail with 2 completely separate single tracks, 1 for Metrolink and 1 for Network Rail, which should be adequate for a 12 minute frequency on Metrolink and a 20-30 minute passenger train frequency on Network Rail, with capacity for freight trains outside peak periods.
It would be difficult to convert the Glossop line to Metrolink without restoring 4 tracks between Ashburys and Guide Bridge and an innovative solution to keep Metrolink separate from Network Rail between a point just west of Guide Bridge and Hyde North. In addition, Glossop and Hadfield are not in Greater M/c, so why would TfGM wish to invest in this line; it would also kill off for good any possibility of re-opening the Woodhead line.
On a general point, Tram-Train looks to be a very complicated and difficult-to-deliver solution for GB, based on the Sheffield experience. The continentals seem to be able to deliver it much more easily. However, there are a few lines in the UK that could be converted wholly to light rail. Ashburys to Rose Hill is one. Squires Gate to Lytham is another. There are other possibilities, but separate from existing LRT networks.