Minutes for Bullock or anyone else on the roster don't need to come from a specific position. Pikiell often goes big to small to big in the middle of a half. The reality is an increase in minutes for Bullock or Omoruyri could come from Nigel Johnson or CJ Gettys or anywhere in between.
My prediction for B1G.......average and range
Sanders 33 36-28
Freeman 25 32-15
Johnson 24 30-13
Williams 24 30-13
Laurent 20 30-10
Sa 20 24-13
Thaim 20 28-14
Omoruryi 14 22-6
Gettys 14 22-8
Doorson 6 10-0
Sure - but I think it'd be safe to say that the minutes are allocated largely on value to the team. That is, the staff is giving the most minutes to players who provide the most value, regardless of the lineup. Given that, if you were to take minutes away from Johnson or Gettys, who would they be given to? Likely, those minutes would trickle down by value - where Bullock and Diallo are at the bottom of the list right now, based on how many minutes the staff has been giving them.
If we had a game where a couple of our guys from 1-3 got into severe foul trouble, the rotation would dip down further into our depth... and Omoyuri would probably see more minutes before Bullock would, because he's above him on the value list. If we went with a small lineup for most of an entire game, and Gettys/Sa/Doorson saw their total minutes shrink to 20 or so combined, then we'd also see a lot more of Omoyuri and probably see Bullock get more minutes to spell the guards.
To your list, it looks like you're expecting us to do a lot of small ball in the Big Ten. Gettys/Sa/Doorson/Freeman would see an overall reduction of about 7.5 min per game (mostly from Gettys), which would go instead to Sanders/Omoruyi. Not sure why we'd go small so consistently - it seems a little counter-intuitive since we have the most height in the conference. Overall, players who stand taller than 6-7 would see 8.5 fewer minutes overall, with only Sa seeing a touch more time than he has so far. I do agree that Sa will probably start seeing more minutes than Gettys, though.