I agree with the open market, ie like his value in a draft pick trade. But if they trade him for ANOTHER guy in a similar situation, then his value remains the same.Thuney trade value now lessened as new team cannot extend him until post season. A huge risk diminishing his trade value.
That being said, I looked over a list of players who are currently franchised and unsigned to extensions and one name popped off that list. And if truth be told, if I had done a modicum of research before I wrote the OP, I would have never suggested a Thuney-Ngakoue trade, but rather a much BETTER option. That being a Thuney - Leonard Williams trade. Better position fit. Better player. Better size. More upside.
BTW- very surprised that I haven't heard this possibility earlier.