And as others have said, there's many more ways to pay respect to the history of the show than by just trotting out the original actors.
Let's hear some then.
A scarf on a random character?
That's really an equivalent to, you know, seeing the people?
In just a couple of years, we here in Indianapolis will celebrate the 100th running of the Indianapolis 500.
And guess what? They won't be running cars in this anniversary race from this great race's long history, even though the vast majority of the past winning cars have been preserved and are in operable condition.
Oh sure, there may be one or two cars that are recent enough to still be active on the circuit, but none of the greats from the past. Those bastards! How dare they call it an anniversary race unless each and every of the surviving 99 winning cars take part in the race itself?
They may as well admit that all they're really celebrating, is the anniversary of the last few years.
Or to more directly answer the question of what some of the "many more ways to pay respect to the history of the show than by just trotting out the original actors" might be...
I can honestly see how they could fully and satisfyingly honor the entire span of the show, and celebrate the spirit of all his past 'incarnations', through dialog alone (in the right context of course), by having the current Doctor simply reminisce fondly of his past.