There's a good Twitter thread from Sean Doolittle about some of the health concerns the players will want to be addressed in MLB's proposal. A few things he mentions:
Worried about the long-term effects if someone gets COVID. "On top of respiratory issues, there's been evidence of kidney, intestinal, and liver damage, as well as neurological malfunctions, blood clots & strokes." Also lung scarring and possible fertility complications for men.
Sharing indoor spaces increases the infection risk, so will MLB make any modifications to clubhouses or other facilities to mitigate this?
How frequently will everyone be tested? Not just players, but all support staff (coaches, umps, security, grounds crew, media, hotel workers, transportation workers) How does MLB plan to get those tests? What's the plan if someone tests positive for the virus?
Will there be added healthcare benefits for players and staff?
What happens if there's a second wave in the fall?
All good questions. Hopefully MLB has some reasonable plans to address these issues, or I'm not sure their plan will pass muster with the MLBPA.