I think it's an excellent idea, for the short-term future?
Modern technologies make it easier for a solo occupant to navigate these days. [Bike riders have already shown us the way]
As for fatigue? How do we think lorry & bus drivers cope? Fatigue has always been an element of the full LDTs, passengers or not. [Again, solo motorcyclists have had to deal with the same issues for over a century]...
I suspect also, LDTs may have to take the form of daylight-only events, for now?
My concern would be, would we need extra rules to allow those with family passengers to compete on an equal footing[!?} to those without?
Would certainly make my job of entering a lot easier, not having to consider another OAP's needs as well?