Ok this idea contains many different things its maybe more something for a separate game mode or mod.
Short:
-5 Classes for every team like in many Tactic Shooters (Medic,Engineer,Scout, Assault,Supporter)
-all of these Classes are similar strong wen they fight against each other.
-Players gets xp instead of evos/credits
-Buildings get XP too (e.g. wen a turret kills a Dretch), and getting stronger.
-every player can use his xp to enhance his abilities.
-players can give their XP to buildings to make them better
-Battlesuit and Tyrant are spacial Units, limited to 1 or X percent or the team.
The Classes:
For the Aliens we got 5 Classes + Tyrant so there must only found out with alien get with job.
For the Humans players got there binds for special weapon sets. In this way, the weapons are divided to the classes + different Armor. On the Armory players only get ammunition, and can maybe switch with another weapon for the class.
Classes can be changed by the main Building OM/RC.
Every Class is similar strong. Expect there could be something like a rock-paper-scissors principle.
Experience point:
Wen a player kills a enemy he gets XP. This can he use to level up his abilities. like defense, attack, stamina, and one special ability per class.
The Ability level can only be so hight as the stage.
e.g. With higher level for attack a player gets another weapon or extra functions for his actual weapon.
Building can get these XP too. A turret which killed many aliens is make and take more damage than a new one. In this way it is more useful to repair buildings. Player can now use there XP to level up the buildings to make there base better.
To get a higher stage players must give there XP to the RC until a certain number is reached.
Battlesuit and Tyrant
To get a Battlesuit/Tyrant a special Building is needed. With these building only one Player per Building can use these class.
It cost much BP that a team cannot build theme to much. And the class requires all Abilities at level 3 or something similar
