BB is 68 not 35. He has won 6 super bowls and is changing Shula for all time wins. IF he stays, I doubt he has the patience for a full rebuild with a rookie QB unless that rookie QB had Trevor Wilson like talent.
THe ONLY path that makes sense is to bring either Jimmy G or Brisset back as they are familiar with the system and trusted by BB. Obviously BB loves Jimmy G and therefore I believe Jimmy G will be the guy. If he can not get Jimmy G or Brissett, Mariottta would be his next choice.
He will use his best draft assets to get a strong DT , WR, TE and LB.
Unfortunately we are without a non compensatory third year pick this year.
UPDATED; John Lynch says niners expect Jimmy G to be their QB. He has usually been true to his word, so now I think the Jimmy G option is less likely