I see now where your question is coming from. It looks like you're going back from four wheels to a tricycle.
Variable wheelbase is all the rage. MIT and Toyota do it.
Put a horizontal hinge, kind of like a motorcycle framehead, at the gray dot. The subframe would be a parallelogram 4-bar linkage with coil-over-shock[s], and a positive stop at the front and back.
I haven't thought out the telescoping bodywork yet.