Am I getting this right: Mariner may have fought in the Dominion War?
Possibly. She presumably has been serving since before then. Last season, we saw a flashback of her in uniform onboard the Quito in which one of her Starfleet friends recounted the plot of TNG's Descent as if it had just happened. Wiki suggests TNG S7 was 2370, and DS9 S4 is 2372.
She talked about serving on DS9, and her holo program has her escaping a Cardassian prison, so it fits.
We will need some clarification on how old Mariner is. Boilmer said she was the same age as him which is obviously a lie.
Someone already pointed this out, but Boimler is probably just wrong. Considering these people have served together for at least a year, there's a lot that they don't know about each other.
I would imagine Mariner is in her early 30s, but it is possible that she had an early start and is younger than that.
But Tawny Newsome is 38 and the characters were reportedly cast so they could be played by their voice actors in live action, meaning we can’t have a serious age discrepancy. Jack Quaid is 29.
Boimler is presumably in his early 20s, so Jack is as much older than him as Tawny is older than Mariner is likely to be. Also, most actors often play younger than their age. Also, I tend to doubt that there is a report of how the actors were cast to be played in live action potentially.
It's inexplicable that Quark's would be a galaxy-spanning franchise. What a seriously dumb idea in service of some very shitty fan service. Bleh.
Even putting aside Quark using Rom's connections to catapult him to a franchise, "inexplicable" is far too strong.
I am not sure it's fair to say that Quark was not portrayed as successful with his DS9 bar. He wanted more than he had, and some richer Ferengi looked down on him, true. But he still seemingly had a fair amount of latinum. Even accepting for discussion's sake that Quark had not been successful during the run of DS9, there is no reason that he could not improve his fortunes dramatically years down the line. Many, if not most, successful real world businesses go through a soft/lean period first. Also, it was clear that in at least some part, the bar was a front for him doing far more profitable shady stuff and he was being kept in check from the shadiest of stuff by Odo. It's very plausible IMO that once Odo wasn't around to keep an eye on him, Quark's business (illegal and otherwise) would be able to blow up. It's also plausible that setting up franchises in other places that would allow him to do shady stuff with no Odo in sight might work well for him.