This will be long but if you are like me, vanilla chosen are too damn easy but this is too damn OP. Through some ini editing and file moving I have given the chosen prime reactions from the ABA mod.

three mods, aside from the ABA mod, are needed
this one https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1633798492
this one https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2132415653
and this one https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1792964849

first, go to the config folder of Repurpose Abilites and open XComRepurposeAbilities.ini and add these lines
+Abilities = (TemplateName=chosenassassin, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosenassassinM2, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosenassassinM3, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosenassassinM4, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosensniper, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosensniperM2, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosensniperM3, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosensniperM4, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosenwarlock, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosenwarlockM2, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosenwarlockM3, AddAbilityName[0]=PrimeRulerReaction)
+Abilities = (TemplateName=chosenwarlockM4, AddAbilityName[0]=PrimeRulerReaction)

next go to the config folder of Vahlen's Mild-Chosen Ruler Reation mod and copy both XComAi.ini and XComGameData.ini and paste both of these files in the config folder of Repurpose Abilities

in order for these file edits to work, have Alien Rulers Use Prime Reactions enabled, and Repurpose Abilities enabled, you do not have to have Vahlen's mod active, you just needed it for the config files

There you go, Chosen now have prime reactions, along with the alien rulers. This is in my opinion the best balance with enough added challenge. There is only one thing to add, if you have Restored Chosen Traits mod, make sure to go to the config folder of that mod, open the XComGameData.ini config, and either delete or mark out the line +ChosenStrengths="ChosenAgile"
this is to ensure there is no conflict of abilities