I respectfully disagree with the premise of trying to build the one line without first considering the 3/4 line. The 3/4 pods are the starting point because of the 4's all being in Omaha or Alberquerque. Teams in those seeds are also harder to bracket for because they are typically all from conferences with multiple teams -- the 16 seed teams are always easy to move around without breaking bracket rules. The 16/16 split is neither a rule or preference from what I understand (the fact that it happened last year - well naturally its going to be a 50% chance). But if it is, I stand corrected, and your analysis is bang on. UK will get the play in, even if they are seeded lower, merely because they are playing closer to Dayton. I do know the committee chair noted that reducing travel for play in's is an absolute priority this year.
The only 4 seed near Dayton is likely going to be Nashville (two other four seeds will be in Portland, one will be in Alberquerque)
So Nashville on Friday will certainly get a 5 - 12/12 matchup.
That means there will be play in for an 11 seed, in either Louisville, Columbus or Nashville. That will come down to fit. They probably prefer to make it in Lousisville, so they can split up the 16/16 games, but at the same time when you consider conference bracketing rules, they may have no choice but to put it in Columbus or Nashville.
And if they have to put in Columbus or Nashville, then the 11/11 and 12/12 play in games are on Wednesday, and both 16/16 games are on Tuesday.
And in that scenario Syracuse would get a play in game.
**** BTW, TV may mandate only one 16/16 game per night as well, so it could be a rule.