The trouble with having Kirk as a holodeck mentor or guide is that Shatner would never have worn it.
Yes, Generations was supposed to be a TNG movie not a TOS one, but we already know Shatner's first reaction even to Moore and Braga's script was to tell them that he wasn't gonna do it because "Kirk is not integral to this script". So I can't see him agreeing to be in a movie where Kirk's role was even less
Certainly Nimoy bowed out under similar concerns that his role was basically a glorified cameo at the start of the movie (^as others have already said in this thread, this was a missed opportunity by the writers given that TNG itself had already established that Spock was alive and well in the 24th century, so Spock could
have been better integrated into the plot!).
I still think the idea that the Star Trek movie franchise had to have the torch passed from one generation to another was a phony premise. They should have just hit the ground running with the TNG crew and used Star Trek VII as an opportunity to revitalize the movie franchise. Draw a line under TOS with STVI and reboot with Picard and crew. The mish-mash of needing to incorporate elements of both is one of the reasons the movie doesn't quite work.