I had that idea also for a long time. You built it up. Fine work. Congratulation. I dream to make it more variable so you can adjust it like a elyptocycle trainer to. One aim is to train your body and train your coordination too because it moves around while you are training. The second is to transform it to a vehicle. I fancy to play with a CAD so you built it in a garage. As a vehicle I think it is to exhausting to do all three works: hand, foot and coordinating for a longer time. So how far did you travel with it already? There should be a handlebars for traveling i think. Because I know how to be modest there could be elektric drive for traveling, adjustable suspension, covering, modular skalability to ride with three and all these ideas of a newbe. So thanks a lot to craft these good ideas.