An interesting and thoughtful post - thanks hatter.
It will be disappointing if our line is not electrified, but personally I'd regard the introduction of tram trains as a significant benefit, on the whole. Hatter lists three benefits:
To offer some balance there are 3 main benefits
1 Every 12 minutes
2 Do not require a public subsidy
3 Electric & modern
To that I would add the much greater convenience of being able to get on a tram-train at Rose Hill or Romiley and get off in the middle of the city - i.e. where you actually want to go, as opposed to Piccadilly. Also, the smaller capacity of a two-car tram-train would be offset by the greater frequency, and you can always hope for double (four-car) units as seen on existing Metrolink routes at times.
The line as far as Hazel Grove is already electrified, of course, and it would make a lot of sense for that electrification to be continued via Chinley and Edale to Sheffield, so that electric Transpennine Express trains can use it.