[Lenin]

Here are some relatively painless ways to show speed-of-light communications:

Episode X: Mal says "Wash, how far away is our oh-so-respectable-and-solvent client? Ninety light minutes? Send him a message asking why the guay his money transfer hasn't come through yet! Me and Kaylee are going out to work on the stabilizer vane again. I feel a powerful urge to hit something with a hammer for three hours. Call me if you get his reply before we've finished."

Episode Y: Mal receives a desperate call from an old acquaintance on one of the Rim Worlds. "Well, they're a light-month away, no need to rush off unprepared. Either it's already happened, or it can wait a while longer while we divert to so-and-so to pick up some heavy equipment of the breaking things kind. Jayne, I want to borrow one of your catalogs, and not the ladies' lingerie one."

Episode Z: Mal has been woken up to answer a call. He's wearing his pyjamas, has bedroom hair and looks half-asleep. His interlocutor introduces himself and asks if Firefly is available for hire. Mal replies that it certainly is, reels off his standard rates and asks what the client has in mind. Jump-cut to the client who says that it's a simple job needing no more than a few resources, and not much time, so a cheap rate would be appropriate. Jump-cut to:

Mal is now dressed, shaven, hair combed and is holding a glass of synthetic OJ and a piece of toast. He asks for a few more details, such as the location of the job. The client names a Border World. Jump-cut to:

Mal is now wearing overalls, his sleeves are rolled up, his hands covered with grease and he's fiddling with a doohickey. He points out to the client that that planet has been under Alliance interdiction since they broke the planet's terraforming in the war, and quotes Serenity's "Sneaking past Alliance frigates and landing in blizzards" rate. The client demurs, and suggests a much lower rate while forwarding a guaranteed reliable fake science mission transponder code. Jump cut to:

Mal has a distinct five o'clock shadow and is looking even greasier than before, except for his hands, which are relatively clean. He picks at his bowl of noodles while he speaks, suggesting that the transponder code won't be much help with landing in a world-wide snowstorm, and quotes a rate half-way between the previous figures. The client sighs and gives in, telling Mal where to deliver the McGuffin. Jump cut to:

Mal is clean again, though damp, and is wearing a bathrobe. He tells the client that it's a deal, sends Serenity's account number to transfer the first half of the fee, confirms a date to drop off the McGuffin and signs off. "Jian gui! I hate these long, drawn-out negotiations with a passion. Kaylee! Can't you make something to make the radio work faster?" "Oh, I'll just rewrite the laws of physics: it'll be easier!"

For extra comedic effect, the client is conservatively dressed in a business suit, immaculately shaven and manicured, and sitting behind an empty desk in every shot of him. The only thing that changes in his office between shots is the ambient lighting as the day passes.

Doing it this way is no more painful than any other piece of exposition, and it would establish the principle of SOL comms in a way never before seen in a sci-fi show. And seeing things I've never seen before is an important feature of watching sci-fi shows for me. It really isn't a difficult thing to keep communications time-lag in mind while working out a plot; no more so than the thousands of other things a writer has to bear in mind.