It seems to me that he may be looking for something other than a partnership, but I’m not very clear either. Let me take a few shots in the dark and maybe I’ll hit one.
This is what I pieced together from your post (which seems to be intentionally vague, so I won’t pry):
- You have an idea which is related to L4D, a TRS game. (Note: It’s Valve that owns the IP.)
- You would like to pitch the idea to TRS, for an unknown goal.
I’m not sure WHY you want to pitch, which is kinda the main point of asking for advice. So I’m going to write a few thoughts on each possible reason and you can look at (click to open) the one that applies to you.
You wish to develop a for-profit game using the L4D IP
You are extremely unlikely to succeed. For one, the owner of the IP isn’t TRS, it’s Valve, so you’re asking the wrong people. Not only that, from the way you write, you seem to be an independent dev (if you’re one at all) or in a very small studio. Feel free to disregard if this is incorrect.
There isn’t anything wrong with being small. Thing is, established companies will usually prefer working with people with a track record and some modicum of operation size, as a means of assurance for management staff who don’t look too deep into it but hold some decision making regardless. Additionally, significance is a factor for filtering out communications (ie Valve may never read your message at all) otherwise any big company would be inundated with solicitations from many people who have no idea what they are doing.
If you are so inspired by L4D, and you have great faith in your idea, I would advise you to create it yourself, under your own IP. This allows you to skip a massive amount of paperwork and communications and not give [the IP + almost all the profit] to Valve, which would be the almost-certain result in the unlikely event of successful negotiation with Valve. Not only that, but by properly reskinning the idea, you will be forced to think about it in greater depth and develop the idea into something more mature and unique.
You wish to develop a fan-game (not for profit)
This is a very prickly task. Again, you’re barking up the wrong tree (Valve owns L4D, not TRS), but more than that fangames are in a questionable legal grey area, and most companies are thus uncomfortable with dealing with that and would much rather just discourage it from the get-go. There have been many different attempts to go about this, but none of them (that I know of) seem to be generally accepted as the “correct” way.
Ignore legals and go ahead and develop.
With a minimum of formal announcement (asking them to initiate talks if they feel like it), you go ahead and make the game, knowing you could be shut down at any moment. It’s a massive risk from your perspective, possibly able to be told to give up all you have already done with a cease and desist letter and various shadowy thumbscrewing that a big company could do to you.
But on the other hand, it allows you to start immediately while you have momentum, and is the most reliable way to make a company that isn’t giving you the time of day sit up and take notice of you, however badly that may turn out.
Make a prototype and use that as leverage to get some formal communication.
A working prototype goes a long way to making a company care about what you have to say. It proves your concept could work, it proves you are able to make a game, and it adds urgency to middle-management folks to pass your message up, by showing you are capable of option #1.
However, there is always the chance of being ignored regardless and wasting a lot of time trying to communicate. Or, being shut down before you could ever do anything.
Make a visual design and/or prototype and use it to gather community support
With enough community noise (coming from people who might withdraw support for the main game, if alienated), any company would be forced to respond, although it may not be in a positive way. So if you gather enough people who are vocally excited about your idea, something will move, one way or another. The downside is of course that it might be considered a show of bad faith by control-freak companies, and give them a reason to crush you as hard as they can. Additionally, it would require you to have some serious charisma and demagogue skills.
You wish to simply let TRS know about your idea, hoping they will be inspired by it
Well, you could post here I guess? If you want them to take anything other than inspiration from it though, you might discourage them from doing so by running into the legal issues that @Kathryn_James mentioned. But if it’s a minor suggestion it should be ok, since people spam suggestions on forums all the time and it’d be really weird if this legally prevented companies from taking up those suggestions. (I’d love for @MissMurder to comment on this since I don’t speak legalese. How should we give suggestions without treading on the unsolicited idea thing?)
You wish to publish the game and you want TRS to develop it
Well, this one’s been settled: TRS has a contract and is not looking for another. I don’t think you would be able to convince them otherwise without some fat stacks of cash. But if you are a publisher and have some financial clout, you could just hire another studio or hire enough devs to make an in-house studio. You can also about IP issues, like what TRS is doing with B4B, which is a rather overt reference to L4D without actually being it.
If you’re thinking of doing dev-work, I’d recommend checking out the GDC youtube channel as it has a wealth of useful information for aspiring devs and small studios. My favourite speaker is the guy from No More Robots. That said, all the talks are essentially opinion pieces so be sure to take them with a pinch of salt.