Here's my take and I'll call bank (it will probably be a brick though).
There isn't really a reason to not sign a 1 year deal like you say unless he wants to bank that 5/200+ mill from Dan's pocket and be a UFA when Bronny will enter the league (he'll be at the end of his career and he will sign for the vet minimum with whoever drafts Bronny). But he can still do that next year after a 1+1 (decline option again) and then a 4 year max from say LAL or whoever. He gets to see how the landscape changes over the course of 1 more season before he signs his final long term contract. He loses a little money, but hey I think his family is looking good on that front. I'm almost positive that Bronny is going into 8th grade this Fall, so all this HS talk is being blown out of proportion. Most kids start HS in 9th grade lol (yes, I understand hoops are competitive before then). I also know the NBA does not permit kids out of HS at the moment, but that is going to change before Bronny graduates HS, and this kid is going to be a stud.
So, I'm sorry to burst your bubble, but I think it's another year in Cleveland (although still with an outside chance of a 1+1 in LA this year) and we're doing it all again next year. The Lakers know this, and that PG is staying in OKC, so they are trying to add these extra picks from random teams (while taking on bad contracts) to trade for Leonard this year, instead of having to land 2 max UFA next offseason, and while keeping more of their young talent. They'll figure out a way to ship out what they need to before next offseason when all they will need to do is be able to offer Lebron a 4 year max deal. Down the line, the NBA will rig the Bronny draft, and Lebron either gets to come home again or get to play a full season inside MSG.