I'm married to a dyed-in-the-wool fan, and have met enough Whovians to know how passionate they can be!
I briefly considered making a Doctor Who scarf for my hubby, but couldn't face all that garter stitch, either!
Given what you've said about his other scarf, it sounds like you're on the right track: subdued colors, long but narrower, something you can work on without a pattern or deadline, a project that's a welcome filler rather than a taskmaster!
I've come across references to a method of deliberately dropping stitches in a patterned way. I believe it makes the finished item longer and/or wider than it's original knit dimensions. There was a mention awhile back on the Yarn Harlot website of a Christmas gift scarf made this way.
There's a "ravelled rib stitch" mentioned here that might work http://www.knitty.com/ISSUEspring04/PATTfrill.html
Amy has an "Elongated Stitch Scarf" under the "free patterns" tab that looks intriguing. And at this site there are some other possibilities http://www.knittingpatterncentral.co...ry/scarves.php