This thread is fast reminding me that there are far too many good schemes to really choose just one!
The Battlefield Line is ripe for extension in both directions, and the surviving trackbed formation at Shackerstone could make for a wonderful recreation of a rural railway junction too.
At the moment it's a "nowhere to nowhere" line and its visitor numbers reflect that in spite of the strong tourism draw the area has - with Market Bosworth station being stuck in the hands of private owners and not likely to change, its not somewhere passengers tend to alight and visit. Shenton, despite its close proximity to the visitor centre, isn't particularly well-known about or frequented, presumably because most visitors to the area don't bother to visit Shackerstone due to it not really having anything to do with the battle, and facilities at Shenton are limited.
At the very least, an extension to Stoke Golding would be useful, to tie the line in with the battlefield story as much as anything - after all, it was supposedly where Henry VII's coronation took place after the battle, heralding the start of the Tudor dynasty. Pretty big part of the story, so to be able to sell a train ride from the (approximate) site of the battle to the site of its aftermath's most significant moment could be an attractive prospect.
The two challenges there are crossing the Fen Lanes junction, which would probably require one, if not two, new bridge and possibly a new embankment, and potentially deviating from the original trackbed at some points where it has been taken for light industrial use. The latter shouldn't be a massive problem given the very rural nature of the route - in fact, there's a pretty large field to the west of the track bed at Stoke Golding which could provide room for a proper terminus and sidings if needed.
