I've played the new class with both with and without zombie mode on.
One thing I noticed about not being in Zombasite mode is that the Zombie threat bar remains, and the Lore items are still dropped, both of which are unnecessary.
I was thinking the game drops you in either with total zombasite infection between everything, in every dungeon with every species — or nothing. It might be interesting if there were a gameplay option where your choices affected whether the infection got released in the first place (or when), at which point it spreads from creatures, in dungeons, across sectors, or because PCs and their henchmen are infected spreading it to critters (had more than a few instances where my party was unknowingly 2nd stage zombasite-infected, they should be spreading it to creatures at that point when they fight in combat, right?) So basically instead of walking in when it's already rampant, having it ramp up during play.
May be too late for that, or if you have the hooks to make it easy that would be a cool modification/addition. Just a thought I had that would make it relevant to act quickly -- kinda like the threat bar runs up in a different color until the virus escapes/is released, then ramps up for how virulent/rampant it has gotten. It makes gameplay center around trying to stop this atrocity before it becomes a worldwide threat.