This may be a problem ( maybe somebody has a solution )
Hope this will make sense
Even though you only have 2 characters fighting at any given time, the way Construct is set up and how you select players all of the other characters will still be in the same sprite and have to be loaded in RAM.
I usually have one sprite called Player and each character and all its animations will be appended a number like walk0, walk1, walk2 hit0, hit1, hit2 and so on, and a global variable called selected will be assigned those numbers 0,1,2,3 depending on which character is chosen so when doing my events I only need to use a single event for all characters Player > play animation "hit"&selected.
Of course, you could have each character as its own sprite and/or spread them over a number of layouts, but with Construct how do you trigger animations without having events for each sprite. It is much more efficient if everything is in a single sprite, but then you may have memory problems of course.
With Flash it was easy, just because you could rename sprites on the fly. Player > play animation "hit"&selected would still work with any sprite/character, because whatever character you select gets renamed to Player