Great work. I found this after looking up a few zombie mods and think this has great potential.
Some things I would like to see to make it more realistic.
1:
No spawns for one.Have like 200 zombies all stuck in one vault some where close to a highly populated area. Have them run to that town and attacking anything that moves on their way there. Your out exploring and stumble across it. Figure you might as well open the door and see whats inside. Then they all come pouring out. Your only option is to run.
2:
Make infection greatly higher.It would be nice if we could have a bite option here so you can get slapped around and not get infected then get bitten but I won't ask for too much, I'd say a 60-70% infection rate works ok.(Is this the percentage of possible infection per hit?)
3:
Only way to kill zombies is with a headshot.This makes all the difference in my book. The head must be crippled in order to kill the zombies. You can cripple the other limbs so they can't use them but I would like to see that the only way to kill the zombies is with a headshot. This would also make it harder for the NPC's to take them out and thus the no spawn wouldn't be such a bad idea.
4:
Once infected always infected.Plain and simple, if your the player and have high endurance(say 10) you get 3hrs to find a cure.(Maybe you find 2 syringes in the Vault that some scientists worked on before the infection took over) If not you die.
5:
Possible way to slow them down.I know the player has a cannibal perk but could we apply that to them? So if I'm running for my life and see some NCR dude doing the same I could kill him and some zombies start munching down on him for a while while I get to safety?
6:
Starvation.When the zombies conquer a town they might stick around there for a while looking for food, check out the general area but they have a starvation clock I guess you could say. Probably something like our FOOD in hardcoe, maybe makes them slower or better yet faster cause they are fighting to survive. First phase would be to wander out and find food, second increase adrenaline, third slower movement and fourth pretty much just stand there waiting to get shot.
7:
Have the zombies wander out.This is probably the most tedious I guess, might have to set a patrol for the entire wasteland but yeah that would be cool.
I said I wouldnt ask for too much but this probably is. I would love to take out the spawning in this to create a more realistic feel to it, having them run from one town to another and spreading like wildfire would be awesome. Forget the infection restrictions, hell make all quests fail when you open that vault, this would be an entirely different game. Maybe this sounds too hardcoe but it's just my 2cents. Speaking of hardcoe I think the only way to play this mod would be to disable fast travel and play on very hard hardcoe mode.
Again though, great work and hope you take some of my suggestions here to heart when your working on this

Edit: Well #3 was pretty easy to accomplish. I simply added a ZombieBodyPartData and made all the zombies use that(That way the dmg on feral ghouls stays the same). Then put the damage multiplier on all limbs, excluding the head, to 0.01. I also lowered the health of the other limbs so you can cripple them. I'm using a save where I'm lvl 26 so might change the head dmg mult to 3 instead of 2, or maybe 2.5, that way you can survive at low lvls with low dmg weaps.
It's kind of funny seeing everyone get infected, it's really spreading like crazy this way.
Right now I'm going to try out #1 and #7. I saw a mod that seemed interesting as well. It's called Wasteland Defense. Let's you place objects around the place and build forts. This would be something pretty interesting mixed with this. I was thinking of a retractable ladder to get you to safety or use a hammer on doors to build some kind of barrier that has health.
This thread kinda died down so hope your still working on this Foxtrot. I hope you don't mind me editing your work, I won't release it, it's just for my personal use.