"The Wounded" is one of my favorite episodes and Maxwell was clearly working alone with revenge as his motivation. I had hoped we would see him in DS9 as a member of the Maquis. Imagine Miles having to fight on the opposite side of his beloved commander. That could be some great story telling!
Since Maxwell was presumably doing prison time when the Maquis was formed, and it's doubtful he would would have been released before their downfall, I really don't see how that would have been possible. After all, I doubt a starship captain who launched unprovoked attacks against someone the Federation has a treaty with got out of prison within 3-6 years.