Very cool concept! I might suggest allowing you to somehow switch between classes, or give the main story a lot of replay value so that the different missions don’t feel too isolated depending on your class. Either that or you could be in a party so that you’d be able to cover multiple missions. In any event, I would recommend finding ways to make the player comfortable trying out all the different play styles before settling with one they like the most.
As for programming, while I can’t say I’m truly an expert, I’ve somehow managed to get by without Parent/Child Blueprints, Tags and BP Interfaces. I’ve mostly made use of Actor Components and Function Libraries instead and it works great. I guess it depends on your preferences.