That, sir, is one of the best ideas I have heard. Awesome. If they did that I would be more than happy to have them just focus on a couple of the Doctors, or cut the screen time down for them, in the special!
In regards to age I had an idea about how they could get around it, but it's longwinded and probably wouldn't fit an hour.
We have a villain, perhaps Omega or the Master or even the Angels, who has decided to mess with the Doctor's regen cycle to make him live to death, so instead of the regens we see on screen, all the Doctors are dying of old age before becoming the new guy. Eleven realised it will catch up to him sooner or later and so has to go back, tamper with time and effectively set something up in each timeline to make himself regenerate so that his timeline can go back to it's natural course. Maybe it turns out every time a bad guy comes along and actually beats the Doctor and causes him to change, it's actually because 11 put them on the trail and made it happen. But in the meantime he has to visit his other incarnations who are under the effects of these changes and they are all older and much changed in their timelines, still adventuring away until they die of old age and he has to go on to the next.
When I thought this out in my head it seemed to make a lot of sense. When I write it out, it doesn't. If any of you can make sense of it, well done
