The premise is similar to the Maquis, particularly as seen in Chakotay from Voyager
. (The Maquis were ostensibly more honorable than your garden-variety pirate, and thus more palatable.)
I would want to know why
a once-respected Star Fleet captain turned to piracy. It seems to be a total 180 degree turn considering that pirates are pretty much the scum of the universe. Explaining such a change would make for an interesting story. Is he/she truly a bad guy? Is he/she actually working for Star Fleet Intelligence or other covert agency? Or, perhaps he/she is seeking someone/something and piracy was the only avenue for finding it?
Just my two credits.