So I've been constantly looking for a way to somehow move objects over a rail.. and I thought... Why not add a rail gizmo part?
The rail gizmo would have an attachment like the winch and would move over a straight line along the part. You can add multiple rails and they would connect automatically. Once connected, The other rails can be edited to have another wire or just have none and allow the first wire to pass through. This could be really useful and would allow builds like Tank tracks, an actual aircraft carrier catapult, Or even cranes!! Hope they add this in SP cuz using pistons really has limits...