thoughs are not really difficulties, just changing values isn’t really changing dificulties.
If anything I would suggest adding a survival mode. (likely a bad idea but all ideas can be tweeked)
[spoiler]concept
survival of the fittest, enemies die faster but so do you a full charged suit only protects against 5 or 6 rounds and a grenade will always be your death, that said it is the same with the enemies with your average alien going down in one or two shots of a pistol and hecu soldiers going down in 3 or 4 shots.
features
weapon limit: you are limited to 5 weapons that said you can drop weapons at any time and pick up guns off the ground, sometimes this is quicker then reloading.
less ammo and health: ammo spawns are halved in amounts not only that but all sources except infinite catches and charger have lower ammo and health
your suit is your life: keep it charge as with out a charge you are only 2 or 3 shots form death.
AI tweeks
h-grunts
changes:
- limited ammo 2-10 mags (unlikely to use all of) have glock/revolver side arms.
- will throw grenades more often but are limited to 2. not all soldiers have them, soldiers with them have them on the model shot to detonate.
new: heavy grunts (see new: means idea of mine highly unlikely to ever happen)
info: human soldiers armed with a m249 saw, they can unload death at anything, but only carry 200 rounds of ammo, after which they swap to their glocks.
note: the saw can be used but can not be reloaded like the m60 in l4d. the quicker you kill them the more ammo you can get.
guards
changes
- more accurate, but more likely to spawn with less then full health.
- in later levels may have mp5’s or crossbows, though are limited in ammo for them having 1 or 2 mags. (will use grenade launcher on mp5’s)
- use grenades from time to time, rarely and generally only have one if they have them.
vortagaunts
changes
- can revive other vorts by shocking them, so gib the vorts unless you want something dead to come back.
headcrab
changes
- can try to turn Gordon into a zombie
zombies
changes
*headcrab may detach from a wounded and try and turn gordon into a zombie
*guard zombies may pull a grenade like zombine’s.
*guard zombies may drop a mag or two from a glock or revolver.
A-grunts
changes
*snark grenades, may throw a snark nest which will walk around for a few seconds then explode showering the area in acid and 1-3 live snarks.
*charge, may charge the player when low health knocking everything out of the way be it friend or enemy.
new: A-grunt heavy
info: an A-grunt with almost tank like armor and two hive hands, is almost immune to any none explosive damage, would only be seen in surface tension and xen.
bullsquid
changes
*grapple attack: will try and grab the player preventing them from running before tail whipping them knocking them down.
hound eyes
changes
*directed shock wave, rarely a hound eye may start charging its attack out of the range of the player only to seen a directed pulse at the player, this does more damage but also hurts the hound eye.
[/spoiler]