You know, I actually talked with a friend of mine a few times over the last few years about making a survival focused zombie MMO. We even had some of the same ideas (including, strangely enough, somehow integrating with google maps to attempt to more easily recreate real world locations).

A few thoughts that immediately came to mind:

I like the different play stylesa and the idea of being able to hunker down, scavenge and whatever else you can think of, as well as working together. I think all of that could lend it to a very immersive zombie apocalypse survival experience. I'm not sure I'd even bother lumping them into defined classes though. I realize that's somewhat necessary given the points system you thought of, but I'll get to the points system in a bit, and I think having it be as simple as load a character and see what you can do would make for a more interesting explorative process for the player. Instead of laying out the playstyles and making them choose when they load a character, let them explore the possibilities without spelling things out too plainly for them.

As far as the points, my first thought it that using them as sort of a substitute for a monthly fee wouldn't work in a real MMO. The costs of developing and hosting servers for an MMO can run into the hundreds of millions of dollars and without monthly fees they just couldn't exist in their present form with persistent worlds. Maybe someday that will change, but for now, it would be bad business to let the people who spend the most time playing (and therefore who are most likely to pay a monthly fee) to basically build up credit by doing so. Maybe you could get around this with microtransactions, but I dislike the idea of microtransactions in general and it would probably work against a realistic survival feel to be able to pay money for new and better items, weapons or abilities.

Of course if you tke away that aspect then it introduces a problem with the boss zombies. At first I thought it was odd that you would include an incentive to not survive too long in the form of stronger boss zombies when you die since this doesn't leave players much incentive to actually try and survive which seems to be the central theme of the game. This is sort of counteracted if surviving longer gets you more play time (though I'm not sure these competing incentives totally cancel eachother out, and it may lead to some wierd behaviour on the part of players), but if you remove that aspect then the whole thing kind of falls apart. Personally, I think it might be a lot simpler if it was a simple matter of everything giving points and when you die it creates a boss of an equivalent level, but that does create balance issues for new players. But if it's at least possible for low level players to escape from or potentially defeat these bosses individually or in a group then it at least makes it fair and can introduce some truly terrifying moments. Maybe you could even balance it by having characters a certain number of levels below the boss, or with a low amount of playtime retain whatever items and weapons they had once they respawn if they're killed by a boss?

I also agree with getting rid of the potential to die when resting. It's a neat idea and certainly realistic, but I think it would piss people off more than anything. Players tend not to enjoy random elements with such severe consequences, especially when there's not a lot you can do to prevent them. Even if you log off in a secure area, if there's the possibility that you can still be attacked and die then most people will find it less enjoyable.

All in all, a good idea, and very well fleshed out. I've wanted to see a zombie survival MMO of this sort made ever since Resident Evil Outbreak was announced (so about 9-10 years or so?) and would definitely play something like this despite normally not having an interest in MMO's. I'm actually surprised that no one has done this yet frankly.

As for how I would play the game, I may join up with some people online if there was anyone I knew outside of the game playing, but I'd definitely lean towards a combination of fortifying a position and going out to scavenge for supplies whether in a group or on my own.