Personally, I'd prefer the Flynn, Moore Tannehill combo. That assumes both Philbin and Sherman endorse their respective past qb's. That way, you maximize your chances of having your franchise qb of the future on the roster. Flynn knows the system and would be a player coach on the field. If nothing else, he'll get the rest of the team up to speed the fastest. I know he has a small sample of work, but he has played at a high level in 2 more NFL games than Luck or RG3!
LOVE Peyton, but at this point, he is no more a certainty than the others to be able to play at a high level, and at best he plays for 2-3 more years. Then we're right back where we started, looking for a young future franchise QB. There's a risk/projection/leap of faith with each of these qb's; there's just a lot less long term upside to gambling on Peyton.
If they sign Flynn, I can't see them drafting Tannehill. Flynn is still a young QB and I would think that they would project him to be the QB for many years here. Now if they sign Manning, I could see them drafting Tannehill since Manning doesn't have many more years left and they would need a QB once he retires.