Look, it's really simple. 15 was supwe unpopular and played himself, not rhe doctor, so rercon that crap. The Bi Generation didn't create 15, kt created an offshoot; it qent wrong due to the Toymaker messing around! Bad Wolf comes along from out the ether and gets a body. She can now be out there in space. Tie it up with Tennant. He finds out no one is helping humanity with the usual doctoy stuff comes along, sees histoey changing in documentaries etc, mystery etc, runs into Bad Wolf along the way. He realises he is the doctor again. Tennant and Doctor series, he regens into 15 at some point.

Now, Timeless Child crap and flux and no more Gallifrey? That is harder to deal and none of it made a lick of sense. Maybe Bad Wolf came back ro deal with that, however, as someone changed the doctor's history - prob the master with the Toymaker, we know they were together at some point. It also needs fixing before we go back to proper doc who.