Most PBEMS have a moderator that sets things up on a "fair" map which usually has people far enough apart that the chance of getting wiped out by turn 50 are very very slim.
Also, knowing that a proximate neighbor is rare, most of the best players focus on infrastructure early and not military.
Personally I never saw the point of early conquest of a human player anyway. Usually the cost in units and time and support is more than the resulting captured bases are worth. At year 50 I still want to focus on tech and crawlers.
Oh and I'm not up for this game at the moment but I could be interested in a couple of months ( so for your next one). BUt give it a couple of days and you should have some takers. I recommend 4 humans as optimum.