Why it wouldn't work
Douglas Adams had massive input into the film, he ensured Arthur Dent was an Englishman, not some Yank putting on a duff accent. He wrote new scenes most notably the entire part with John Malkovich and he ensured his close friend Stephen Fry became the voice of the Guide itself. To envisage a film interpreted by someone else is never going to live up to the fans expectations, just ask Eoin Colfer who has been inundated with abuse after trying to resurrect the series with his offering. With such a cult following it is hard to take up the mantle showing the right amount of respect and making the correct decisions about what to leave out the film.
Why it won't happen
Martin Freeman said quite quickly after the original that a sequel was off the cards, with his fame increasing and that of Zoeey Deschanel the budget would likely have to include hefty fees for their main characters. But more than that is the issue of it commercial success, the DVD sales were not enough to make up for the average viewer response in cinemas.
What to do next?
Well as you can only enjoy the one movie I'd suggest you get a big mug of tea and read the books from scratch.Unless of course you are an exceptional scientist in which case get back to work on that ressurection maching and get the man himself back here to sort out this dreadful mess, his fans are waiting.
So Long and thanks for all the fish!