Traditionally the role of the male companion would be to provide the muscle. There was always a male companion with the 1st Doctor because he was ‘frail’ and the production team believed they needed a younger actor to do the stunts. When it came to the 2nd Doctor they actually gave him two male companions.

You are correct, Adric was a solo male companion in the episode Keeper of Traken because Nyssa wasn’t traveling with the Doctor. She was just another background character in that story. That is until she appeared in Logopolis as the Master’s hostage. She then is saved by the Doctor and becomes his companion.

Funnily enough a script was in the works by Paul Abbott during Series 1 which would have revealed that Rose was the product of an experiment by the Doctor in forging the perfect companion. But Abbott didn’t have time to finish the script and thus RTD rushed through the episode Boom Town.

I smiled at the audacity of that. I used to hate that bit from the tv movie, I now don’t care but at that moment in time I was intrigued if Moffat was actually going to go there. It was all a bit of an insider joke to the fans who’ve seen the tv movie.

Except for that one time when the Doctor was shot by a Dalek but decided to stop the regeneration mid process by transferring the excess energy into his severed hand. RTD pretty much undid a regeneration which is about as least sacred as you can get.

This is how I perceive the Hybrid.