This industry has multiple forces pulling at it.
1. Airlines that want to max revenue and minimize cost
2. Employees that want a livable wage to do the same job (having flown RJs and narrow bodies and heavies I feel confident in saying that in the general picture its the same job)
3. Pax that want to pay a low price

Scope will not get put back into the bottle.Sorry.
What all mainline pilots and regional pilots should do is make the cost of RJ flying go up. Same work rules -same per diem- same benefits then address the pay issue.

example-Say 10 year captain pay on the RJ should equal 10 year FO pay at the major or some such formula.There are better minds than mine that can do this formula.

RJ guys get better QOL and pay.The financial incentives for a mainline carrier to farm out flying decrease and ML pilots see the reward in more pilot hiring.

This takes a unified effort from ALPA and other unions as well as mainline and regional pilot groups. The old line-we must hang together otherwise we will surely hang separately is very apt.

All pilots in a 121 environment must be at the same level of safety.That includes duty time,meals and rest.Every airline that flies passengers must be a real airline .(a VP Flt Ops at a previous company used that line on us).
The flying public must be assured that when they buy a ticket on UCal (example only) from India to Bakersfield all the crew and all the pilots are part of the same culture of safety and oversight-and operate under the same standards

Again Scope IMHO is dead.More importantly it may not be a good business idea to have.Some cities cannot feed a A320 or 757.Asking the ML to either cancel that city pair or operate at a loss on it with bigger planes does not help anyone. Making the cost of such an operation higher will make airline mgmt less willing to send 3 RJs instead of 1 A320.

This is what National Unions and Pax groups should be fighting for IMHO.
An industry leading contract at Mainline X does no good if half of your domestic flying goes to the lowest bidder.Instead of trying to kill off the RJ or acting like its a pariah on the industry ML pilots should bring them into the fold.A certain National Pilot Union is/was very apathetic on this concept-to the detriment of all pilots.This must change.
my 02