There are some interesting benefits of using a whole motorcycle though.
1. It should be better sized for the sole task of maintaining hiway speeds than a typical car ICE.
2. It offers complete redundancy. If the car breaks down you have a bike, if the bike breaks down you have a (short range) car. If you are an adventurous experimenter you might appreciate that
3. It should bypass any extraneous licensing. You don't have to license a special trailer that you use once a year if you already own and use a small bike. You don't really have to worry about legalities as the bike is already DOT/EPA, and bike dollies won't draw much attention.
I think the hitching/control issues are completely solveable for someone familiar with the systems intended purpose and who drives accordingly. This isn't anything for production though, just an idea that might be useful in a fairly specific set of circumstances.