Sorry not to have any great info for you, but I see you're new on iorr, and didn't want you to feel totally ignored.
I'm sure you've done a lot of research already, but I found (web search only) this, of potential interest:
"One day in early 1982, Mick Jagger dropped by the horse-racing track Manor Downs to view some thoroughbreds. Millikin was also the general manager of the track, and he passed a videotape of one of Vaughan’s performances to his old friend. A few days later, Stones drummer Charlie Watts called Millikin and asked when he and Mick could see Vaughan play. Millikin hastily arranged a private showcase party in New York City at the Danceteria nightclub in April. Aside from members of the Rolling Stones, only a handful of people showed up, but a photograph and an article about the party appeared in Rolling Stone magazine. Rumors spread that Vaughan was going to sign a deal with Rolling Stones Records, but Jagger passed, saying as many others had that the blues just doesn’t sell."Stevie Ray Vaughan: Lone Star Rising, Guitar Magazine - 08/18/2010
Other than that, and his association with Sam Cutler (of whose 1969 role with the Rolling Stones you're probably aware), what leads you the believe Millikin had a specific "role" vis-à-vis the Stones?