I was thinking about this.
I would suggest a toggle between two options for each character in the party. For my fighters I would just set it so I pick their reactions going into a fight so I don't have to stop and click if they want to take an opportunity attack every time the option is available and for casters be able to toggle it so I can choose if they use a reaction and which reaction to take into account a changing battlefield. Do I want to use shield, or should I save a counterspell? If I know I'm using counterspell but there are multiple casters I may want to pick and choose which caster I counterspell and if the one I don't pick goes first I want to be able to say "no" to counterspelling his spell because I want to focus on the other caster who I feel is a bigger threat.
