Would it theoretically be possible to space out a Charge Stove to take a standard 135mm rear MTB hub or is it a terrible idea?

If so fallback may be to run it fixed with a front hub on the rear with a bolt on velosolo cog

What spacing is the Charge Stove? 110mm? Standard bmx or 120mm track?

Lots of bmx hubs out there, also lots of flip-flop track hubs.

It’s 110mm – BMX spacing. I’ve picked up the frame cheap and got enough bits for a build but wanted to avoid cost of getting another rear wheel built up given that I’ve got 2 spare 26″ MTB wheelsets which are now surplus to requirements.

Spacing it an extra 25mm apart is probably right at the very edge of sensible. You might get away with it…but you also might wreck the frame. Weight up the cost of buying a new frame versus building a new wheel and see what makes sense.