It would basically be like how they did the alternate site player pool and COVID taxi squads. You designate 2-5 players who are eligible to be added to the 28-man roster even if they aren't on the 40. They would get paid something for that status (if not full 40-man pay). Difference is you'd be doing it for a whole month instead of a just a short-term outbreak. Except taxi squad players actually didn't even get paid (just per diem) or get service time. I'm guessing alternate site players who weren't on the 40 only got their regular minor league pay (which was subsidized in 2020). The owners would probably never go for something where they had to pay more than 40 salaries.
But in truth it's probably not even that big a deal to subject them to waivers. If the Phillies wanted to make Ronald Torreyes and Cam Bedrosian their extra guys and then they got claimed in May (or sooner, if sent back down) that's the same risk as any other time, if they want them in the bigs. Players with options would still be protected. The other alternate site rule was that once you DFA'ed someone you couldn't re-sign them even if they cleared, and that would be fine too (i.e. either forcing the team to keep the guy or making it easier for him to move on).
