11. He seems the most like me, as does Rory actually if we're talking about companions, plus there'd presumably be Amy or Clara there, both of whom are very, erm, nice women.

In fact, can I just be Rory?

I like your thinking and as I loved McGann and Eccleston, it wouldn't be a hardship travelling with them until they became Tennant.

Three for the price of one - love it.

Wouldn't that take about 500 years?....

If you went from mcgann then travelled permanently then yes, but if you were in a 'drop off inbetween adventures situation' and he was only coming back for you every so often it could be possible.

The ideal situation for multiple doctors would be to get picked up by eccleston. As far as we saw he and tennant aged roughly in real time with the series, so if eccleston picked you up around the same time he picked up rose or later then you could stay with the doctor permanently and assuming you didn't die in an adventure could travel with eccleston tennant and smith without ever having to go home.

In the audio adventures, Charlie begins her adventures with 8 but concludes them with 6. Its all terribly confusing but great fun!

Exactly, it's time travel and anything's possible. You could say an emotional farwell to 11 eleven then bump into 1 the very next day.
Would actually love to see this on screen where a companion leaves their doctor and then does an adventure with a past doctor who's meeting them for the first time. Wev'e kind of already had it with river in the library but it wasn't quite the same as she met multiple doctors all out of order and presumably had already had adventures with future versions of 10 (considering he seems more familiar with her by the start of time of angels) so it wasn't really the same.

It would be great if a companion who wev'e seen with 'their doctor' leaving the doctor either permanently or just temporarily and then bumping into, and having an adventure with a past doctor, who just takes a liking to him/ her for the same sort of reasons his future self does, with the companion feeling awkward, and trying not to mention anything about his future.

Could even be cool to see this the other way around, say for example Capaldi land's in a place where an early series 7 version of Amy and Rory are, and they see the tardis, think the doctor has turned up for them, and run in only to find the 12 and Clara inside. Then for some reason the story requires them to stay together for the episode and all the while Capaldi's hearts are breaking just to be around them and Amy is constantly trying to get info out of him as to why this future version of him has replaced them. Obviously at the end he'd have to drop them off home, and swear them to never mention his visit to 11 the next time they saw him.

With writer creativity and actor availability their are so many possibilities

5th I want to be part of the Scooby Doo gang.

Also 5 seemed like the big brother type. As in an older brother... not watching me pee in the shower

Great question. I think I'd pick 11, 5, and 4, in that order. 11 would be the most fun, but I can't help feeling he has more chance than most of getting me killed! 5 would be safer, and there were plenty of companions, so it would be a sociable journey. 4, like 11, would be a lot of fun, but I can't help feeling he worked best with one close female companion - I'd feel like a third wheel, or to use the technical term, 'Harry Sullivan'.

Worst choices would be 6 and 9 - we'd just end up being sarcastic at each other all the time - or the War Doctor. Never mind the constant fighting, all that 'No More' for years on end would grate on my nerves.