I'm going to let you in on a little secret here. Once an airline has employees at an outstation get enough seniority and better pay, they will cancel their contract and give it to "another" company.
By another company I mean another Delta company. It really is the same company, but Delta will cancel ground contracts after 5-10 years and give it to another one of their "companies". It will probably go back to Delta or maybe even Mesaba. Either way employees start out at year 1 pay.
After 5-10 years Delta will probably give it back to Pinnacle. All this whole time the same employees will be do the ground handling, but will have to start over again at year 1 pay.
This is all done so they don't have to pay employees for being there for a while. Safety means nothing to them, just cost savings.
The only way to fix this is the government to mandate Delta has to use its own employees, or for Delta to use employees of the airport. But it has to be one of those options. Otherwise, they will just shift back and forth to start people over at year 1 pay.