I love the idea, because it would be good if they based the prestiges on kills or maby how many zombies youve killed. Stats would be kinda cool too, like a leaderboard. Headshot count overall, Kills overall, Use of each weapon like they do now for multiplayer but with zombies!
The idea would only be good if it doesn't affect what you get in game. If you need to be level 40 zombies to use a wonder weapon, screw that, it would suck. If its just there purely to show skill/time spent playing, go for it. And because it would only be worth it if it just looked pretty, it probably won't get implemented, treyarch aren't going to programme something pretty pointless, even for aesthetics! it would be a waste of their time and money. Sorry, just my view, keep zombies as zombies, and not multiplayer, multiplayer on CoD i always find laggy, full of hackers, and actually really boring (CoDs been the same game in everything but appearance since 2007 when CoD4 came out, its a repeat apart from map changes and weapons dressed up to be a different weapon. This game i'm buying for campaign and ZOMBIES. if multiplayer is any good, it'll be a breakthrough for CoD for once and a big bonus, but i doubt it, sorry.
High rank doesn't mean a good player, a bad one can also reach high ranks with failing like 1000 time on lvl 5. I'm more for when u do some thing great like lets say 300-500 heatshots in 1 game u should get a title or camo for the online, so u have something than not even a leech can get by just dieing over and over again, it would be pure skill. This way they link MP and zombies a bit together without them merging, u will get more ppl from the MP coming to zombies and also the other way around.
Anyway a rank system should never be linked to guns u can get and can't if u don't have the rank, it would suck even with the pros for the first couple of games, maybe even more like 50 first games.