However, I'd rather see a new alien race than a modified one. I just don't really like changing vanilla stuff for no good reason.
My purpose is to modify the original balance that I always found poor, so I will change the foundation before construct new floors
Also for each alien race, define two (or more) categories, make other categories appear later in the game, so that some times battles are as usual, and other times battle are a little harder than expected
I also think to this, but I dislike the idea player can't immediately see there is something different. So I must change color of aliens if I change their armors, and because it is so difficult to do I prefer not try for now and work only with the differents races, and their distribution in UFOs with mixed crew. But maybe I will change some damage type of terrorists, and give aliens possibility to use thing other than plasma, and mix terrorists type.
Here the modification I planed to make :
sectoides lose HE resistance, but gain AP and PL résist, STUN, MELEE and SMOKE vulnerability. They also have double HP.
Purpose = with so low HP and armor, resistance and vulnerability as no interest at all because the weakest weapons are already near overkill. So, more resistant to rifle and pistol, but not to explosives weapons. Their poor armor make them suffer injuries by any weapon, despite new resitances. More HP is only for make them able to withstand at least one shot and not already be OS. Vulnérable to stun and melee is for match their weak appearance. vulnerability to smoke is because they breath.
cyberdics gain melee resitance (like all mechanical thing in my mind) but PL vulnerabilty.
Purpose = original one is not bad, but plasma weaken make it counterpart with the fact it is resistant to anything else and I assume it was designed for strike against human and not againt other alien equiped with PL weapon.
floaters gains many resistances : AP,HE, stun and smoke.
Purpose = This for match the fact they are partially mechanical and bionic. I assume they are designed for terrorise humans, and so, their new resistances make them able to do that. Becoming protected against human primarily weapons, but they are not really powerfull anyway because of weak armor and lack of HP. They can be shot by any heavy weapon, but also by autofire or multiple fire of weakest ones. Difficulties to stun or asphixiate them is because their bionic improvements, and give a capture of them more challenging (we should not easily catch a terror weapon). With advanced weapons like LS or PL, they become weak aliens only usable for scouting, interesting allies for strongest ones like snakmen or muton, by the fact they can fly.
reapers gain better frontal armor and strong resistance to HE and melee.
Purpose = they are too weak even against weapons they are not supposed to be, so the frontal armor help them (because they often face their adversaries) and match the fact they are design for offense. Resistance to melee for let no chance to anyone they succeed to catch, and HE resistance to match the fact they are supposed to be realy resistant (and for reduce the 4 square malus HE for them). Already weak "under" armor make it weak against HE or especially IC which are thrown to explode at his feet (obviously it need some throwable IC weapon).
snakemen loose some armor at side and rear but gain more at under. They gain resistance against all weaponanry supposed to produce heat : HE, LS PL.
Purpose = with moderate armor and HP, they are strong against weak weapons of all type, but easily catch by heaviest. Heavy AP humanmade weapon should be nice, especially in is back. So the idea is to force player to try to ambush them. Because they are not vulnérable to HE and with a better under armor, grenades aren't be the best option against them. I think their "foot" resistant because continuously rub on the earth.
Chrysalids gain slight resistance against anything and huge vulnerability to HE
Purpose = I always loved the choice made in TFTD about tentaculats, which are best shot by HE but make it difficult because they run to be close to you. So I choice to make chrysalid nearly immune to all kind of damages thanks to their strong natural armor, but, vulnerable to HE. It is also a good allies with snakemen which they are not vulnerable to HE, and need accurate AP weapon. So for strike against them two, you need varied weaponary.
mutons loose resistance to AP but gain better armor, slight vulnerability to STUN and smoke.
Purpose = with their full body armor, they seem to be protected against everything and have only a small weak point in their face (so the lighter front armor). My change make nearly no change against AP weapon, but make mutons better against all others. So it need really heavy anti-tank weapon for hunt them, but of any type. Maybe stun (or mind control) could be a best option because it is in fact their only real weak point.
celatid gain strong resistance against LS and PL, slight better armor, immunity to smoke but vulnerability to AP
Purpose = It is like if this creature can absorb energy so she's nearly immune to energy weapon but can be pierced and cuted easily, so no advanced weapon useful against it (and because this creature went in the long term, it could be annoying if you don't still have some no LS or PL weapon in your backpack). He or IC could work, but moderate HP and armor negate the weakest ones.
silacoid gain better under armor lose HE vulnerability but gain melee vulnerability
Purpose = this armored thing has only a melee attack and is slow so it isn't really dangerous. Make him only weak against melee is for make something like the only way to kill it is to stab it with powerful cutting device. But it is dangerous to approach him. (I plan to add some melee weapon like thermal lance of TFTD)
etheral gain slight resistances against anything except IC and melee.
Purpose = weak in melee because it is obviously their only weak point, and IC because this type of damage is underuse in this game and I think it could be interesting to use against these, because as they often fly, it will not be so easy to burn them. I also like the idea their strong power can't help them against flames. (And I never understand why the original game give them a strong resist because you nearly never use IC and by the time you encounter them, you have logically abandon IC weapons by long time ago).
sectopode have no change except resistance in melee
PAL and hoover remove the IC immunity, gain melee resistance and lose resistance to acid.
Purpose = IC weapon use very hig temperature able to melt heaviest armor, I don't undestand why original game make IC so weeak against anything because in reality IC is really powerful, and to use with extreme care. The acid defense removed because I see no reason to make PAL resistant to a kind of "alien-movie" acid, and because there is for now only one rare creature which use it. I plan to use the acid damage type for new weapons (of all types) which could be really "armor piercing" and could overleap other resistances by have this tag. A powerful anti tank rifle could have a "acid" damage in place of AP, only to simulate it really use ammo which can pierce armor (like HEAT). So I will work on acid armor of all thing when I add something like that. (For now, the idea is to make huge resistance to this for no armored aliens, and weak for heavy armored. So, a acid-AP weapon wil do nearly nothing to a sectoid -totaly run through it- and huge damage against a sectopod)
At last, I hope the 200% vulnerabilty to smoke make some aliens able to fall unconscious if they stand in smoke (and humans so, force them use mask or helmet). But I don't know if it can actually work ?