Of course, but therin lies the rub. Flying at mainline stays at mainline (until and unless mainline gives it away of course). But any new flying regionals "gain" can't possibly be a lasting gain for anyone's company or seniority list. If DAL/UAL/ETC agree tomorrow to outsource the E190/195 or C series, some regionals will of course get that flying. But it won't last unless they are committed to permantly being the low bidder. To get today's RFP for growth AND to KEEP tomorrow's RFP for existing flying. That will mean competing against other regionals who will always be just as hungry as you for growth, upgrades, seniority list advancement and the like. So the seat count would go up, and maybe even with a temporary raise/upgrades, but in the long run it will be back to today's status quo and likely less. As an added bonus, there will be fewer better jobs to go to, by choice or necessity. And at the end of the day the sector as a whole won't be any more secure.

That is why any additional flying to the regionals on behalf of a mainline partner is bad for the careers of both. The quick high of regional upgrades, which to no small irony and no small part is looked upon as a good thing for the PIC building opportunities to eventually go to a mainline carrier for many (and even helpes drive SJS based low bidding in the first place) becomes a self fulfilling prophecy that drags down the mainline and all regionals anyway.