I agree, in any large scale battle situation where ranged and melee fights are occuring simultaneously there will be FF issues, add in AOE weaponary and "cone of fire" effects and it's going to get very interesting if your in the hotzone even if players are trying to be careful.

Penalising players for FF in such circumstances would be unfair, however excessive/repeated FF incidents perhaps should be punished but its a very fine line to be walking.

As for players from different faction collaberating to "feed" each other RP or even "achievements", that simply can't be stopped by GM ingame without extensive player Log reviews to spot the pattern of exploitation.
Two players sitting in the same room IRL playing different factions participating in this type of behaviour simply can't be detected as a deliberate exploit until much after the fact.

Speaking about FF again, in one of the online shooters I used to play FF started to be a big issue, it was abused very often by low rank players to kill their higher rank teammates in order to get their fully upgraded weapons, it was very infuriating as everybody was helpless.

However, the devs didn't react to complaints so finally a group of top players decided to execute an excessive teamkilling operation in order to bring the problem to the attention. The next day appropriate measures were introduced by the devs against abusive TK (automatic kick from servers after 3rd teamkill and temporary ban on this server), the action was very effective and the problem was solved.

Gotta drop a name bro, i doubt it had thousands of players playing at once. The issue that will occur often is that people just arent in control over a teamkill. Like a shot fired before someone ventured into the attack radius of the missile, or casting an AoE (for instance a sorc casting a malediction) and people who know jack shit about what they are walking into dying to the last man.

Should the sorc be responsible (and by extension punished) cause people willingly went into a pool of death due to their own lack of knowledge of the game mechanic? I dont see how thats fair.
As it stands the issue of punishment is a very tricky one.

Drop a name? It was Bullet Run, a small, niche but very cool shooter. No, it didn't have thousands or even hundreds of players in one place that's why the situation may be even worse in EC which will be much bigger.
I'm afraid you have only two options here Djemo, either you will give high penalties for excessive TK or you remove FF totally. Otherwise I guarantee that you will die due to TK as often as Your enemies' fire or even more often.

Problem being how we label "excessive" and how excessive can accidents really be in an environment where they will not be a rare occasion. If we go too excessive some heavy weapons will just become obsolete since noones gonna use a potential banhammer over their faces.
As it is with the lower dmg allies will receive from your bullets id say lighter firearms (bolters/shootas etc) will be easy to work with. If someones putting in an entire magazine into an ally that person should be punished accordingly. The problem arises with balancing the punishment of heavy ordinance, and not completely erasing its use by making it a massive risk to use.

Never said it's gonna be easy. THAT'S WHY I SAY FUCK FF

That solution doesent rub me the right way personally. Id hate to see 5 Plasma Cannons unloading into a melee slaughterfest and while everyones being blow to bits the marines are just standing there unphased, cheering on the blobs of plasma imploding beneath their feet.

So yeah the devs are gonna have a field day balancing FF if they put it in (which i hope they will).

What about having FF but at a reduced damage rate to team mates? It would still dissuade the "plasma can volley" type abuse you are talking about but would provide a buffer for true accidents. It would have the additional bonus of making it more obvious if some one was team killing as they would have to put in more work for the kill.
As for Req abuse I just don't see a good answer that doesn't cost a metric sh!t ton of man power to do.

(Isn't there a FF thread to put this on? feel like we're hijacking this one a bit.)

You know what would be the best solution for FF abuse? Turning all your characters into a grot in the Ork faction. Exessive abuse of the FF mechanic will turn all of your characters into grots for x amount of days. Continue to do it, just keep adding days on top of each additional sentence.

Shooting and abuse of grots is encouraged.

That's exactly what devs were mentioning.