Hey Fatshark people and the other people visiting this forum.
I Came up with an idea for a new game for you guys so here’s my pitch.
Basically Vermintide but set in the Warhammer 40.000 universe. No one has done a really successful WH40K game yet (Cyanide Studios tried), but Warhammer Fantasy Battle already has two great game series (Vermintide and Total War Warhammer). WH40K is also the more popular of the two (at least when talking about the board game versions) so it already has an expansive fanbase.
The Game could take place in a Forgeworld that’s besieged by an Ork Waaaagh! and/or a Tyranid Hive fleet. Your task is to defend the capital city that still stands but is heavily outnumbered. Exterminatus is for the moment out of the question because of the strategic and economical value of the factory planet. Each of the 5 playable characters has a different agenda for being on the planet, more of that later.
Here’s what I came up for the characters and what is their purpose for being on the planet.
Space Marine Sergeant: Sent to rally the defenders and help with the tactical and strategic point of view, and as a last resort to evacuate those who can be saved if the city’s to fall.
Ordo Hereticus Witch hunter: Sent to the planet to dispose off the corrupt and incompetent planetary governor who didn’t respond to the threats quickly enough.
Imperial Guard Ogryn: One of the guards"men" belonging to the planetary defence force, trying his best to stave off the coming invasion.
Vindicare Assassin: Sent to take out the Warlord leading the Waaagh! / the Hivemind overlord of the Tyranid Swarm.
Eldar Farseer: On a mission to destroy the hidden webway portal on the planet before the enemy might find it out.
Everyone must come together if they’re to complete their tasks.
The Game would consist of 5 Acts, the first 3 acts to be 3 maps each, 4th & 5th act a single map so 11 maps/levels in total.
Act 1: The Party must help the Farseer to destroy the webway portal if they want him/her help.
Act 2: The Party must accompany the Witch Hunter to confront the corrupt planetary governor who’s been seduced by The Great Enemy (Chaos). The Levels woud also have corrupt imperial guardsmen as enemies in addition to the regular orks/tyranid enemies of the base game.
Act 3: The Party must rally the defenders and help getting back the strategic key locations of the citys defence perimeter to set up for the oncoming siege.
Act 4: Withstand the onslaught of the invading horde/swarm. A 20 minute Last Stand mission where you fight waves of enemies and assist the defenders (NPC guardsmen, turrets, heavy weapon positions etc.) on different locations of the perimeter where help is needed. If the enemy reaches the gates and manage to break though the mission is failed.
Act 5: After successfully defending the city the party now sets their sights on the leader of the invasion and tries to cut off the head of the enemy. A Map where it ends on a multi-phase boss fight that concludes the campaign.
Here are some of the roles I was thinking for the characters:
Space Marine Sergeant: Versatile and a bit tanky hero with speciality on upkeeping morale and buffing friendly characters.
Ordo Hereticus Witch Hunter: DPS class with access to AoE flame-based weaponry, also debuffs the enemy to take more moral damage.
Imperial Guard Ogryn: The Only one with enough brawn to handle heavy weaponry (plasma cannon autocannon, missile launcher etc.), also naturally tanky and has an AoE taunt, shoulder charge, footslam that knocks back etc.
Vindicare Assassin: Specialices on single targed dps and marking the enemy to take more physical damage from friendly characters.
Eldar Farseer: A Psychic caster that can help the party with positive powers like health regen/physical resistance or conjure up an eldritch storm to tear up the enemy, essentially doing lots of AoE.
The Game could take a step back into a more ranged combat (a.k.a shooting) based playstyle but still retain the visceral close combat. Enemy types could consist of a mixture of enemies that try to get close to the players to hit them in melee and also have the shooty types, this way the gameplay is mixed more and force the players to utilize the terrain and cover more.
Enemies are easy to pick up from an already excisting list and lore, here are some samples:
The Orks go to war
Ork Warlord
Ork Meganob (essentially a chaos champion candidate for in-game)
An Ork Killa Kan, a monstrous bipedal machine of death (to use as a monster type enemy)
The Tyranids
Tyranid Swarmlord, a biotitan spawned only to kill and devour, like all tyranids.
Tyranid Lictor, stealthy predator
Tyranid Carnifex, a hulking biotank
/end rant, feel free to spitball ideas about this would-be project 
I have more ideas on loot, armor, wargear, drops in-game etc. but too tired to write any more after making this post for 2 hours 
