TL;DR
Since Aliens don't add anything to the game since .15 one is tempted to just turn them off in most of the games (except for deathworld).What ?
So, why not add some usefullness to them which gives a nice buff to .... lets say ... trains.Alien-Fuel. Or Biter-Fuel.
* Fuel Value 200 MJ
* Vehicle Acceleration +250%.
* Vehicle Speed +100%
Maybe made in a Raffinery, as result of a recipe out of ... 1 Alien-Drop-Thingy + 20 Light Oil (to give Light Oil a use other than making solid fuel out of it).
Edit: Why 200 MJ? To make it desirable for Trains and stuff, not for burning it for power-generation.