Or you could get the former actors to play themselves again. The rest of the world sees one Doctor, acting out multiple personalities, we see those personalities as each different Doctor.
Expensive as hell, but you could have Doctors 5, 7, 8, 9, 10...and maybe 4 and 6 if they agreed to behave, wear a wig, and lose a little weight.
.. would have to recast 1,2 and 3 to get all 10 of them. It worked out well with 1 int he five doctors IMO.
Unfortunately, it's very unlikely Chris Eccleston will ever reprise his role as the 9th Doctor. Which is a shame. It would be great to see him again someday.