5 half bottles of sauce at my house would mean I had 5 bottles of sauce I really didn't like in the first place so mixing them would be my last attempt at trying to get something I liked before tossing them out. No need to simmer.
Last time I was in that position, my (then 19 year old) son volunteered to mix up a sauce, and I told him to have a blast. It turned out GREAT! Unfortunately, he's not one to write anything down, so we'll never re-create it. Anyway, he didn't simmer, just mixed it all together.
I keep wanting to try #5 Sauce, ...
I keep wanting to try #5 Sauce, but never seem to run out of bottles in my pantry. You can't go wrong mixing in a little Sriracha and meat juices (from resting/slicing) along with whatever sauce(s) you have. Maybe even some rub or vinegar if needed, and simmer if it needs reduced.