I feel like that part might have been too coincidental that they happen to run into that same guy, but still maybe better than what happened with Phasma. In general I think holding someone at gun point and making them do something on a computer is not the most dramatic scenario. In ROTJ they're attempting to storm the bunker and blow up the shield generator that way, in ESB the empire is coming in with walkers to blow up the shield, etc. Oh well, not a big deal in the grand scheme of things.
I'm probably one of the few that don't believe Phasma ended in a compactor. If so, why not show it. It wasn't even a deleted scene.
As far as Finn and Phasma dueling, not sure about that, didn't Gwen say in an interview that the Phasma armor was heavier that a normal troopers and that she can barely walk in it.. If you pay attention in the film when Phasma walked it was loud and clanking .
We also don't know if the riot trooper armor was specially designed for that fight scene because that stunt man looked like he knew martial arts. So we can't assume Phasma's armor could've moved like the riot trooper.