Good idea, but I think that would be political suicide. You also have to be careful when judging the morals of the past by today's standards. Murder, rape, and theft have always been abhorrent, yet there hasn't been a single age where they haven't happened. All that's changed is societies attitudes to the crimes and those who commit them. I would say that the fact that we currently see what we did as an empire as bad, is progress. I also wonder whether that played a part in its eventual collapse?
We should of used the Commonwealth as a place for our former colonies to get genuine help and support. We should of done better with places like Israel and Iraq, where we essentially forced 2 or more different cultures into one country. Or with Ireland, where separating it into 2 countries has caused chaos for generations.
We've had ample opportunities along the way to get things right, and have consistently failed. Attempting to apologise now wouldn't change a thing, and we no longer have the resources or political clout to help in the ways our former colonies actually need.
Here's an interesting question. We're all getting hot under the collar about what the British Empire did hundreds of years ago, and believe it's current incarnation should apologise. Should all the counties that made up The Allies of the Second World War, apologise to Germany for what happened to Dresden? We currently define any avoidable civilian deaths as a war crime, so was one committed?
(My apologies, I think I've been playing devils advocate a bit too much this afternoon. But it is food for thought, no?)