As limiting as 22 minutes is at times, I think there is a lot to be said for that format. I'm not convinced that making it longer would automatically make the show better. In some cases, yes, they could spend more time on some plots and develop more, but with the extra time comes the risk of viewer inertia. It might be the case that the pace of the show wouldn't work quite so well if it had to keep it up for 45 whole minutes!
Having said that, there are examples that it could work -- the double-episode Company Picnic works very well when viewed back-to-back. If they had used it sparingly on a few 'specials', that would be a nice compromise for me.