I'm not entirely certain about what you mean by travel adjust. Do you want to be able to go from - say, 80 mm to 100 mm travel while riding? Can't really see the point of that. Reducing the fork at the compression end would only have an effect when fully compressed. And if you get there, most people would wish for a bit more travel as opposed to coming up against a hard stop. Reducing the travel at the extended end will change the fork and the head tube angle, almost the whole steering geometry. And lower the BB some. And change your fit on the bike. It would probably kinda-sorta work if you want a FR/DH bike to handle less sluggish on the flat, but steering geometry would only be one of several issues encountered when using a bike entirely outside its intended purpose. If my interpretation is right, then I don't know any fork that'll allow that. And while possible, I can't visualize how one would build a travel adjust feature. There's a fair bit of force to deal with when you hit a bump.