I currently drive a Challenge car on the street - with the spring rates changed and ride height adjusted. Not that hard to do and quite liveable. Would I drive it across the continent? No. But for a rip on the back roads through the mountains it's just fine. As for the CS values. Maybe you are right but I personally would have difficulty justifying paying the current prices when you look at what is available for the same or less. And I don't know if the CS is desired as much as an iconic collectable - aka F40, Countach, etc. - to push it higher than it currently is. It's just an opinion so no need to get underwear bunched up about it.
Ferrari doesn't issue titles in the U.S. The government of the state in which you live issues titles. And there are companies that specialize in getting titles for cars without titles, often vintage cars or hot rods. Can a Challenge Car be titled in that way? If it meets current road safety requirements I don't know why not, although I gather states vary in how tough it is to title an untitled vehicle. In any event, I don't think you need Ferrari's permission to try.