I've always wanted to see a Gary Seven/Questor crossover myself. They basically have the same mission, after all. And I've always liked to imagine that The Questor Tapes
took place in the Trek universe.
But unless CBS buys Universal, I don't see it happening. At least Greg Cox got to hint at it in Assignment: Eternity
; Roberta mentions that she and Gary helped retrieve "the Quasar tapes" or something like that. And then there's the Emil Vaslovik pseudonym in Immortal Coil