Isn't it the quality of the story that is important, not some fan check-list of things that certify that the show is showing the proper amount of respect for the old series?
I don't see having a quality story and bringing the Past Doctors back in some fashion, however briefly, as being mutually exclusive.
They're not mutually exclusive, but neither is having a quality story and not
having past Doctors return. It would be cool to have some of those actors back, but not having them back doesn't automatically mean the result will be disrespectful crap. Just as having them back wouldn't automatically make it a masterpiece anniversary special.
"Canon is only important to certain people because they have to cling to their knowledge of the minutiae. Open your mind! Be a Star Trek fan and open your mind and say, 'Where does Star Trek want to take me now'." - Leonard Nimoy