We need compat with these entropy zero 2 NPC mod: https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2876350981
It adds a few more headcrabs such as:
1. Glowing version of normal,fast and poison headcrabs.
2. Xen heacrab that is basically reskin of a normal one but with design closer to hl1 and lore saying that normal headcrab from hl2 and this xen headcrab(hl1) are different headcrabs
3. Xen fast heacrab that is fast headcrab covered in green glowing liquid (different from glowing fast headcrab)
4. Arctic fast heacrab that is just darker
5. And i guess most interesting, temporal heacrab that is poison heacrab but that is able to teleport (this one can be controversial since we never saw zombies that temporal crab does.

Also it adds lots of zombies:
1. Glowing ver for each zombie (glowing zombine uses xen grenade instead of regular)
2. Arctic fast zombie that is darker just as his headcrab
3. Normal/glowing/xen(with xen headcrab instead of normal) gonome (i guess it could be same as zombine from normal/xen heacrab but very rare
4. Xen headcrab variation of each normal/zombine zombies
5. Xen fast zombie
6. Their own zombiegaunt(normal vortigaunt and xen ver that is closer to hl1 design) that is acting similar a bit to normal vort but more aggressive and willingly to get closer (it has ver with both normal and xen headcrabs). Since there is already zombigaunt addition for headcrab takeover it can be done like that: normal headcrabs will cause vorts to turn into these zombiegaunts that crawls on the ground and shoots yellow energy, while xen headcrabs will cause vorts to become Entropy Zero 2 zombiegaunts.

Anyway, i hope i didnt forget anyone and i hope author will see this and take a note for a future.