Kharitonov is too high level for his first fight back.
Who does he fight first is the question. Considering his age, last run, and ring rust I would give him a simulated Rank of #29.
Unlike the other older guys in UFC HW he has been out of comp for a while.
<the below assumes they have resonable access to the Bellator and M1 rosters/rankings and rosters will stay the same through Fedor's comeback career (they obviously wont)/it's just a rough draft of a reasonable arch>
START
1.Volkov (skip to #2 if Fedor won't fight a Russian)
2.Ortiz (or Grabowski if they can't convince him to move up)
3.Kharitonov (or King Mo if they have less M1 access than I think or he won't fight a Russian/Should be his first fight if he only does two non-UFC fights.)
4.McGeary (or Kongo if he won't move up)
5.Davis
SIGN TO UFC
In the meantime they need to work on getting higher HW and LHW to extend Fedor outside of UFC. Between Bellator, Samurai, and maybe M1 they should have more than enough reasources. Travis Browne is someone accessible, try for him.