That's why the crew should be enforcing the bag limits. One person is only supposed to have 1 carry-on, and it's supposed to be a relatively small size.
Generally it's one carry-on and one "personal item".
Yeah, and the personal item is supposed to go under the seat in front of you.
Often the "personal item" is another suitcase. If given the position of power, I would decree that if your carry-on or personal item has wheels on it, it's not a carry on and must be checked.
I´ll get my duffel bag. Hope I don´t bump into anyone already in their seat.