I thought about that, however, the problem is that the characters simply do not receive any input, so creating a variable will change nothing, because the events like LeftMouseClick will not even execute. The only character in the scene that is capable of receiving input is the one specified in the GameMode in DefaultPawn Class (created upon the game start).
I was also thinking of a rather quirky solution to that (maybe anybody here could suggest something more convenient? ). I could create an invisible Actor BP, which instance would be placed somewhere in the scene and it would handle all the input input and distribute it to corresponding Characters. This should work, but might become problematic when the game becomes more complicated and multiplayer gets implemented.