I noticed you're missing Ray Chapman.

I cut off the list post WW2 when standard sets came out, there were several before that

He does hold a special place in MLB history.  He's the only player to die of injuries received on the field.

Would Luis Valbuena count? He wasn't signed with a team at the time of his death in 2018, but he had played the year prior and was still active as a ballplayer.

Very sad. Lots of car crashes. Wonder if they were flying around in sports cars.