That would be Tee Martin...although I think his stock has soured a bit after UT wouldn't give him a sniff and USC seems to be offensively challenged this season (95th in total offense).
My Personal Top Candidates:
1: Mike Norvell: Currently the HC at Memphis, Norvell has had good success with the Tigers and is known as a good recruiter in the AAC. Currently his class stands 47th in the 2019 rankings which places them first in the AAC. Memphis also has the #6 overall offense in the country this season.
2: Seth Littrell (HC North Texas): 40 years old and has had experience under Mike Leach, Kevin Wilson, and Mike Stoops. Currently has North Texas as the #11 passing offense in the country with a record of 22-16 at North Texas.
3: Major Applewhite (HC Houston): Another young and offensively minded coach, Applewhite is said to have burned his bridge to Texas while serving there as QB coach. Taking over at Tom Herman left, Applewhite has been able to sustain their success all while having the #12 overall passing attack in the country this season. Has served under Nick Saban, Tom Herman, Charlie Strong, and played QB at Texas from 1998-2001.
Stay away from Dino Babers (HC Syracuse): An innovative offense mind that came to the forefront with his 'Falcon Fast' offense at BGSU, Babers has seemed to struggle to recruit to Syracuse BUT has gotten a lot out of the players that he does have. Going historically, their classes were: 43, 53, 54, 56, 52, 49, 48, 78, 75, 66, 73, 51, 60, 54, 58, 64. Babers appears to be about what Syracuse has historically at Syracuse and does not push the needle forward for them recruiting wise traditionally speaking. I think Babers would not be a bad hire BUT Purdue would not see much increase from where the program is currently UNLESS Syracuse is just that hard to recruit to. I'd go with proven recruiters AND offensive minds like the 3 I listed above.