Part of the problem is the idea that mainline pilots are superior to regional pilots. Several of our captains have thousands of hours more flying experience then many mainline first officers. Why would they give up their pay, seat and job security to be stapled behind someone with years less experience?

If you really want to merge both groups, then both groups will have to want to merge. Regional newhires will jump at the chance to be stapled, but the senior half of most pilot lists will not. They'll fight it. Without their cooperation, it will never happen.