All the stuff you'll need to carry around in order to be able to safely
drive the vehicle on roads after landing would need to be carried as part
of the airplane, making it heavier and lowering its payload. This
includes the extra weight used to make the vehicle crashworthy (assuming
you would like to survive a battle between you and a Toyota). And all the
stuff you need to fly with would need to be carried while driving on the
ground - this means you'd be dragging the wings and tail all over the
place. You would probably not be carrying fuel in the (detachable) wings,
so the fuel tank would be in the empenage, which has weight and balance
consequences.


I don't think those electric vehicles made for surface streets (basically
golf carts) have any safety features.
Maybe this aircraft could find a similar loop hole.


The tradeoffs would make the engineering much more difficult than you
suspect, and the result would be sub-optimal in all motion regemes. Put
another way, for the same performance, you'd spend lots more money, and
you'd be better off having a cab waiting for you.

I agree that the result would be less than optimal in both aspects.
I think that would be a minor price to pay.
Start with something simple...single seat, perhaps.
I'd be looking for something that could carry me (175lbs) 100nm @ 70mph,
then scoot me along another 30mi on the ground at 45mph.
I don't think you need much to achieve that kind of performance.

Let's not give up the dream yet!