Nope, a good alien builder will build a spawn or two outside the base for backup.
Sure but this is countered by the fact that it's rather hard to kill a dretch in one hit without damaging the egg. About the only weapon I can think of is the MD and at best you're probably only going to get a couple of kills before either a goon comes to rescue the egg or you miss a shot and dretches is running around everywhere.
Also, sometimes, especially in Karith and Transit, you just have the aliens spawn-camping thanx to the terrible layout of the default human base...
Well that's a problem with the map then. Make a topic asking the maps to be changed. I'll guarantee you that all the replies you recieve will be along the lines of "build some rets then", "don't feed aliens before you can move base", etc, etc.
I would really find it good to have invincibility right after spawn that ends the moment you hit the attack-button or 2sec after the spawning, which ever comes first.
Ok, how about this. Humans are s3 and attacking the alien base the aliens have almost no evos. The aliens thanks to their invulnerability have a few choices. The grangers can escape from base easily because the humans are unable to kill them while the dretches get a free shot and can block all the luci shots.
Honestly the only times that you actually get killed straight after spawning is either when your builder has built a bad base or when you're about to lose and the other team is in your base. In either case I don't see how "spawn camping" makes the game either unbalanced or less fun.