Just make the Star Wars galaxy our galaxy in the future, problem solved. people put too much weight on "a long time ago, in a galacpxy far, far away ...", it was only added to give the story a fairy tale flair, if the narrator is in the future and ina different galaxy the line can remain without contradicting that the Star Wars galaxy is our galaxy in the year 12.475.
A horrible event wiped out all live in the alpha and beta quadrants except for a small fleet of Starfleet ships exploring god knows where. Starfleet seems to be primarily human, so the few vulcans, betazoids etc. contributed a little bit to the "new human" genome, but their features vanished.
It's a stupid story and shouldn't be told, but it is actually easy easy to merge the Star Trek and Star Wars universes, they're both sci-fi/fantasy hybrids were pretty much anything can happen.