Do not make it too difficult..there are shed loads of good , quite new air con EMU's available for a wonderful Corby type service. Could be some great negotiations there with the ROSCO's on price as a buyers market.
It is this half hourly Market Harborough to Leicester market that gets me - yes I know it is a good catchment area and all that , maybe it should be 2 trains an hour ...trains an hour "best fit" ....(i.e on the slows or semi's), with some peak quality fast calls. ?
Yes, there could be some really good prices on the EMUs but at the cost of one TPH to stations further north, and the inability to run genuinely fast services to Derby and Nottingham in the peak.
The huge economic benefit of running an extra 1TPH and the faster services to Derby and Nottingham could outweigh the saving you'd get on a micro fleet of dedicated EMUs.
You'd have to spend millions on infrastructure costs to reduce peak journey times for Derby and Nottingham so my view is that the additional cost of buying EMUs that are compatible with the bi-modes would be well worth it.
If all of the existing four trains per hour could run non stop from Leicester to London, you'd have a much deserved journey time improvement for London services from Leicester and further North. Even if one of these stopped at Market Harborough, you'd still have faster services.
Stations further South could be served by the new fast EMU services two per hour, with one splitting at Kettering to provide an additional bi-mode slow service per hour to connect the stations south of Leicester with the ones north of Leicester. This split service would also provide the 2nd train per hour for Market Harborough.