In a previous suggestion, I mostly spoke of decreasing the Drivatar population in Horizon Solo, and while I still think the Drivatar population should be heavily decreased, this suggestion is another possible solution to keeping the Horizon Festival vibe intact in free roam while removing the annoyance of Drivatars overcrowding the roads and/or smashing into the player.
Basically, there should be an option to ghost Drivatars in free roam at all times, much like how other players are ghosted in Horizon Online. The same can apply to traffic as well, and this ability to ghost Drivatars and Traffic should also be separate as well as be toggable for those who don’t mind the traffic and Drivatars in Horizon Solo, or those who prefer one ghosted and the other clippable.