Ilike Kinga, and also believe he may be a better 9 than MK.
But I think 7 is where we are definitely lacking depth. KK in his very limited opportunities at 7 in firsts was a long way from where he needs to be (not that I am ruling him out because of that). Mortimer has played mostly 6, although the development of his kicking game in a short time this year suggests to me he can make the transition. Outside of those 2 there is no real option. On what Robson showed the second half of this year he was a priority signing and will start there next year without a shadow of a doubt.
At 6 the options are Mortimer, Feleti and KK who have all proven their ability in the position at first grade, plus the signing of Humble.
Kris Keating, Mitchell ,Robson or Mortimer could all play 9 or 14 if required, and likely do a good job.
Really, the resigning of Kingston would depend on releasing one of MK or Mitchell, not signing Robbo. And much as like Kinga, you can understand the retention of the other two.