Hey, this is a nice layout, indeed.
I've been thinking about a very similar one myself.
What I don't like about the above posted draft at all is the pit lane. That should be place across the road on the left hand side of the track, where there is enough pavement to roll in and out, without the need of a bridge. Furthermore, the pit entry wouldn't feed from the racing line out of the roundabout, if place on the other side of the track.