Well, Cons might...Plecos might...you'll need hiding places for any of them...Red Devils will probably hold their own...Dempseys might, and Texans might. However you will have to add filtration and change water more often. You are also going to have to remove the Jag for a bit...let me explain:
1.) Quarantine new fish for one month.
2.) Remove Jag.
3.) Add decorations.
4.) Introduce newbie.
5.) Put Jag back in about a half hour later.
This way the Jag doesn't have a concept of "his" territory because the markers have changed. This may reduce aggression. Be warned, though, if any of these fish are adults, they may not be friendly!