So recently I discovered while trying to make something like this-:

https://www.google.com/search?q=single+drive+axle+locomotive&client=firefox-b-d&sxsrf=APwXEdeWv6f2i1-TYhVfsH8DjprKOdXQwg:1680381311975&source=lnms&tbm=isch&sa=X&ved=2ahUKEwicwL-ZxIn-AhX6QPEDHR9kAvUQ_AUoAXoECAIQAw&biw=1920&bih=927&dpr=1#imgrc=pv4Pk3JREpnIpM

-that you can't make a single drive axle steam wheel, and I thought "well, this sucks :(", so why not do exactly that? Maybe do it like if only one wheel is connected, then just have another type of piston that only connects to 1 wheel, like this except horizontal:

https://www.google.com/search?q=the+rocket+locomotive&client=firefox-b-d&sxsrf=APwXEdfxep8R2E913eAALnP-dD9uVGU_LA:1680381630110&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiShJmxxYn-AhUkSvEDHeqsBkwQ_AUoAXoECAEQAw&biw=1920&bih=927&dpr=1#imgrc=YoYxuERBSq5c0M

That's all I have to say, i hope you guys add it though! Us steam folks would love you 4ever <3