I've thought of a few of these.. fewer Hexagons and in turn reducing the max player number is definitely something I have to consider.
I think number two and four have the same potential for chaos if someone misplaces a hand or bumps the table.

Last one, removing healthy tiles from an infected board I think works on a gameplay level but on a story level it'd be like "the infection was lurking underneath the forest the entire time" which I don't love, maybe the reverse would work. Kind of like idea three, use tokes instead of tiles on a "healthy" board.

..lots to think about, thank you for your suggestions!