The character of Vash was designed by writer Ira Steven Behr who created her for the series specifically to be the perfect woman for Picard after Patrick Stewart's request for more "sex and shooting." Around the fourth season, Michael Piller, the show's associate executive producer, inquired about marrying Picard to Vash to provide some new story dynamics. The studio executives killed the idea of marrying off the captain. The shipboard marriage idea survived in the fourth season episode "Data's Day" where Miles O'Brien married Keiko Ishikawa. Like Picard, Vash is an explorer with an expertise in archaeology. She is an adventurer, a female Indiana Jones. In the episodes where she appears, this beautiful brunette, with her beguiling smile and blue eyes, manages to charm not only the good captain of the Enterprise but the omnipotent Q as well. Vash is Bacall to Picard's Bogart. Watch Bogart and Bacall in the classic movie "To Have and Have Not" and then watch "Captain's Holiday." In December of 1998, Patrick Stewart was quoted in the Calgary Sun as saying "I personally like to think Picard and Vash had a very active sex life. I can't believe Picard just read Shakespeare up there in his room all those years."
In my opinion the Vash character is a gold mine of untapped potential.
Edited to add: About 'Qpid' Q proved in the episode:
Q "This human emotion, love, it's a dangerous thing, Picard and obviously you're ill-equipped to handle it. She's found vulnerability in you, a vulnerability I've been looking for for years. If I'd known sooner, I would have appeared as a female. Mark my words, Picard, this is your Achilles heel . . . You deny that you care for this woman? Believe me I'd be doing you a big favor if I turned her into a Klabnian eel . . . I was just trying to help . . . You would have me stand idly by as she led you to your destruction?" To which Picard answers an emphatic Yes!
Picard
"I'm surprised he wasn't too busy gloating over his victory."
Vash
"He was right about one thing, Jean-Luc. As ridiculous as it was, his game did prove you still care."
Picard slides closer to Vash on the couch gazing into her eyes while tenderly stroking her cheek. "I may not share my feelings with my crew, but I do have them."
Actually there is canon that supports the notion that archaeologists behave the way Vash does. In canon, before meeting Picard on Risa she spent five years working as a personal assistant to Professor Samuel Estragon, an archaeologist who's work Picard knew. It was Professor Samuel Estragon who hired the Ferengi Sovak to aid in his explorations, especially in situations that weren't quite ethical. Moreover, Picard isn't surprised at all and is amused by the idea. (3rd season episode Captain Holiday.)
Also in the 6th season episode "The Chase," Picard's own mentor Professor Galen comes aboard the Enterprise wanting Picard for a bit of muscle and even trying to bribe him with a priceless, rare archaeological artifact.
GALEN
"... I'm sorry, Mister Picard. But that information has a price --your agreement to join me on the final leg of this expedition."
PICARD
"For how long?"
GALEN
"Three months. Perhaps a year. If we had a starship and complete diplomatic access -- a matter of weeks. But we'll have only my shuttle, the transports we can arrange, and our combined talents."
PICARD
"Why can't you do this without me?"
GALEN
"I'm not a young man. There will be hazards along the way. I don't want my own inadequacies to jeopardize the completion of this work."
In this episode Professor Galen is operating exactly the way we were told that Professor Samuel Estragon did and the way Vash did. Therefore, it is a believable extrapolation from series canon that fieldwork in interstellar archaeology can be a somewhat rough and tumble, wild wild west like business.
Warmest Wishes,
Whoa Nellie