Not sure how you expect to move up from 6 or 7 to 1 or 2 without including any of our actually good assets. Noone's giving up much for Knox, Franc, Jr. Smith, Elf.
Gotta give to get.
Otherwise C's don't make as much as they used to, due to a change in hoops style and a C glut. And the glut means most teams don't need a C. Plus the cap likely to come down to the 'Rona Virus. Also, overpaying Mitch some, if necessary, isn't a bad thing since we squeezed him on the ultra-cheap for a few years. Hell, were still paying Noah $6M and Taj more than that. We can afford $12M - $15M for Mitch. And if the market isn't there, we ,might get him starting at $10M, which could be another bargain. (Though I was willing to include him in a deal for Tangelo -- we need a starting PG more than a future starting C).
Since we're likely at best a sub-40 W, marginal playoff threat, I'd start Mitch this year. Let him take his lumps and learn to control his fouls. Develop a rhythm and rapport with the starting unit. RJB, Mitch and whatever rook will be our core; let Randle adapt his game around them if he wants to stick. Obvious needs are shooting and playmaking, hopefully coming from the rook and a FA addition.