OK. But don't all the drivers occupy pretty much the same space. Aft of the front wheel. Forward of the engine/trans. Followed by the rear wheel. I can't think of any modern bike liner that is different and am not sure how driver location should be addressed or if it should.
If we are discussing bike 'liners then I would agree that most, if not all, have the driver in fron of the engine, behind front wheel. But I don't think most in this discussion have limited their comments to bike 'liners only. I haven't.
Ideally the driver is in a reclined position. Not prone or supine, not erect as in a sprint or midget.
Driver should be as close to cg as possible. Either end outside the wheelbase is not very close to the cg.
But, like I said, it is up to the designer/builder to decide whether to bet the drivers life that an accident will not result in a situation that severely damages the cockpit of the vehicle.
The designer/builder must also accept that a sanctioning body may not approve their design and may pull approval at any time. Entire classes of cars have been relegated to storage because of rule canges, etc. NASCAR, IRL, F1 all have done so in recent years.