Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

It has been done, though admittedly on larger engines. By having dual control valves that essentially switches the steam line and exhaust for reversing, while also having a spare R/C channel and servo set up to "nudge" the crank off of TDC/BDC to get it moving again.

Or you could just have steering only and no reverse, or perhaps even no R/C at all, like a typical free release pond boat, as was so common in years past and even still today!