I think I was counting Johnston already being out with her groin problem.
If everyone was healthy I'd like to see
Morgan
Rapinoe-Lloyd-Pugh
Horan-O'Brien
Klingenberg-Sauerbraun-Johnston-O'Hara
Hope
I agree on Horan ahead of Long. She produces a lot more offensive chances, although I expect Ellis to start Long. Rapinoe being healthy is a big "if". Her being fit and ready to excel at this level is an even bigger "if". I'd be surprised if she starts any more games in this tournament, although I could see her subbing in if the U.S. is trailing. At this point, I like Tobin Heath a lot more than Rapinoe. It sounds like Johnston should be good to go in the next game. That is clearly a big upgrade over Engen. Also gives them a weapon in the air on direct/corner kicks - an area where they could use the help.
If everyone is healthy, that leaves them some good talent to sub in for the last 25 minutes of a game - Dunn (or Pugh), Rapinoe, Horan (assuming Long starts), and Press. That group can definitely add offensive spark if they need it.
P.S. I know you meant "Brian", not O'Brien.