This sounds really cool, nice initiative.
I would love to be part of this (I think I would prefer to drive the camera car, if I am invited to participate at all).
I suggest having multiple persons for at least this job though, since you can't always be online. It makes sense not to have 5 different video editors or something like that, but for this particular job it makes sense to me.
Also I think the camera car drivers should be able to choose their car themselves based on their personal preference since they have to be good, consistent and reliable with the car (keep up behind the roadtest car on twisty roads etc).
Also, I propose the hosts should have distinctive looks compared to the average TDU2 model. Something like one host wearing an afro if there is one, so you can tell immediately who it is.
Yeah, that sounds like a good way of handling that part. Except maybe film a characteristic corner on the timed lap (like gambon where some stars go wide and across the grass before the finish line).
I agree with having a race test and choose the fastest person to be The Stig. Maybe also have Stig's Cousin for Offroad cars or whatever.
Has anything like this been done before?