If Wiggins was the exact same player he is now but was 19, had played in college or the G League last year and was in this draft I'm guessing he'd go number 1 over Cade. He was a decent player for GS last year. He's just overpaid and his development didn't come anywhere close to what was expected.
It is my understanding that teams normally arent going to discuss with each other what their motivations/plans are for trading picks. If they just want to move the pick I think they can get more in return for that pick elsewhere. On the other hand if Detroit has decided to take Green or Mobley or someone else #1 overall and they are sure Houston will take Cubningham #1 overall, I guess a free pick at #23 and some minor salary savings from picking at the #2 slot is better than nothing, but... The problem for Detroit is making sure that Houston takes who you want them to take so that you get your guy at number two. As stated, i believe discussing intent on pick trades is not normal converstion, so as Detroit you either have to place unusual trust in your trade partner and have an abnormal conversation about intent with your trade partner, or you have to hold your breath that Houson drafts who you want/expect them to draft. In that instance, if i'm Detroit, I'm not sure that a single late first round pick is worth the uncertanty that you would be introducing with respect to the more important pick at the top of the draft.
I dont think it is as complicated as you think. If we really want Cade then we just let them know to draft him for us as part of trade proposal. In return, we will draft who they want at #2 and #23 and complete the trade.