Getting back to the topic, I have an ideas in my mind.
A mod which is the doom's equivalent of "Wrath of Cronos" mod for Hexen. Just like WoC, it would have various classes, each having their own unique arsenal and the unique skills, strengths and weakness. The classes could be as follows(but they can be different if desired).
Soldier: This would have standard issue weapons. He would be good at closes to mid range combat. Only Basic abilities like grenades, lasermines etc.
Marksman/sniper: Weak at close range but very powerful for long range combat. Arsenal would include stuff like Sniper rifles, Railguns. Abilities could include cloak, slowmo, sticky bombs etc.
Engineer: This class could have unorthodox weapons like freezegun, lightning gun, flamethrower. Abilities could include stuff like ammo crafting(like mana regeneration in WoC), setting turrets etc.
Scientist: This class would be focused around using bio weaponry. Weapons could include stuff like poison bombs, biorifle(UT style). Abilities could include stuff like medicine crafting(healing), stun bomb, hallucination darts, steroid stim(temporary berserk mode).