Portals aren't light-speed unless Ella can run at light-speed because she surely was dodging those portals left and right in the Deryl Arc. I'm pretty certain that Ella cannot move as fast as Tiffany in her light form. Portals are fast, but not that fast!
In a fight to the death, he wouldn't, What she wants basically is a sparring match with his position on the line. That match would be time limited. No one's going to watch them fight for hours so it would result in a no contest, Zach can save scum against Nico for that long if he was able to do it against the 7th and Indra as suspected.
Nico's probably about to be or already is a Captain. The monsters invasion has probably made it that the Captains are now Admirals on some One Piece shit, and the Lieutenants are now Captains, working with their old units directly for their old Captains. It seems the team pairings were created based on group synergy. They would probably continue that line of strategy even if Lieutenants were promoted to commanding their own units. I wouldn't be surprised if MC(or turned down for Micheal instead) ended up being able to become a Captain, and lead his own H.E.R.O team eventually if he stays with H.E.R.O. It could even be multipathed or polled who we work under: Nyx, Malik, Henry, Lucius, or Zach.
This story still has an extreme amount of thrill potential if WW wants to extract it.