I would only make this suggestion because it's come to my attention since I brought Kira Hime (my dober girl) home. We have two Siamese cats who are less then pleased at the way she wants to play with them, and rightfully so.
My mother is visiting with her "7lb. Taco Bell Dog" at the moment and this is another area where I am speeking from with first hand knowledge.
Both dogs love and like each other, however Kira is the equilivant of a Mack Truck and does not undrestand the potential of hurting the little pup while they are playing. I have trained her (for the most part) to lay down while the Taco Bell dog jumps on her face, bites ner nose, ears ect.ect.ect.
Kira loves it... She's like... "Bite my face, Bite my face!!!"
Then Kira will get excited... and stand up....
"Alright no more playing now!"
However both dogs still want to play...
Constent supervision is needed!!!
I would feel horriable if Kira hurt (or KILLED) the little thing while just playing, it would only take one "good chomp."
A 70+ pound Doberman "accidently" stepping or wanting to "play" with a 2.5 lb. Yorkie could be or would be an "EPIC DISASTER"!
Broken bones... Injuries... god help them if the playfull dobbie puppy "nips" or bites too hard playing...
What if the Yorkie is on the floor and the Dobbie jumps off the couch or bed and....
In a perfect home this would be just that... Perfect...
However it has potential to have a very sad outcome.
Meaning you wouldn't be able to keep your new Doberman puppy because the two dogs are not compatiable as companions. Or your Doberman could searously hurt possiably kill the little Yorkie.
I would suggest waiting until the Yorkie has had it's last breath and until then hold off on the Doberman Puppy.
Maybe adopting a senior Doberman with less energy and play,play,play would be a road to travel down?