@Comte Pseudonyme I like your idea of making the alien behavior more distinct. I also think there’s another way to create new aliens while still technically still the same species of aliens, that is having alien ranks being not only a separation of gear and weapons but also genetic implants:
For instance, a generic Sebilian is just another combat platform to the Praetors, and as the creatures rise in rank, they will be given different genetic manipulation to make them more and more varied based on different species of reptiles:
>lieutenants can spit poison like cobras and have more snake-like, more slender body with head flare and fangs
>captains can have shell plates that act like riot shield with a stockier body, with beaked head like a turtle
>commanders having an extra melee attack with a jaw like a crocodile and tipped with alien alloy augmented teeth as well as all other abilities of their lower rank counterparts
While the Caesans can be manipulated for their role as fodders, pilots and low level psy troopers:
> Caesan pilots due to the need of controlling motherships during long space transits have completely degenerated legs with their fingers sub dividing into arms. Being able to wield heavy weapons like rocket launchers on their anti-grav supports
>Caesan Hivers have themselves fully made for being thrown into the meat grinder of war. They have their psy ability modified to have multiple bodies sharing the same mind. Which means they’re a hive mind squad that acts like the soldiers in FEAR.
>Caesan psyker have their bulbous head crackling with a power field that weaken enemies around them and suck away morale every turn. They’re protected by a layer of power armor.
Things like this will show the alien being nothing other than tools for the alien overlords and a grim glimpse of humanity’s fate if we bow down to the praetor. Even a more upgraded Reaper is possible. Where their head and brain is completely replaced by a scouting drone, giving them the ability to wield multiple weapons at the same time, something like Endless Space 2’s Cravers. When the body is too heavily damaged, the scouting drone can detach from the body and attack as the creature’s second phase.
More aliens would be really nice, but I think we could top other games in the same genre by having more non-humanoid aliens. Something sorely lacking in these kinds of games. But if Goldhawk is lacking in time this is the next best bet.