I'm thinking about grangers....
Aliens born from eggs, don't them?
Who places eggs? The granger.
So Granger should be like... ehm... a she-alien, while combat classes should be he-aliens.
So.. here is the GRAT IDEA: sex!

What about making impossible for grangers to place eggs if they are not pregnant?
We would see grangers running around asking for some alien sex (imagine a granger-tyrant sex :roll:

)
Humans could build a special structure named "condom distributor" or maybe a "contraceptive pill cannon" and make egss placing impossible.

This is a great idea... isn't it?
