Your conclusion that it would be to train to Consultant regular GP level (i.e. no specialisations) is wrong, though, assuming you can find a Consultant regular GP in the first place - just get them to teach and the students will simply progress to Consultant status (unless they have a half-learnt specialisation holding them back, but even then they can still improve their abilities so learning time isn't wasted).
Normally doctors will progress to Consultants over time (or by doing stuff, I'm not sure exactly); even if you grab all junior doctors at the start of a level they should all be Consultants at the end of the level wether you teach them or not.
What I'm proposing is that this progression will stop at Doctor level, unless they have a speciality as a Surgeon, Psychiatrist or Researcher, which I think will help to avoid situations where your non-specialists become untrainable by Consultants with the skills you want to pass onto them.
The problem with that is that then you would never be able to gain new Consultant GPs, unless that were added as a new speciality (of sorts).
Actually, thinking about it I think the simplest solution might to just remove the learning restriction of the original game, so that Consultants can still be sent to learn whatever skill(s) are currently being taught. Basically the first consultant you drop onto a training room should become the teacher, and all other doctors dropped into the room (regardless of their level) will progress towards learning any specialities they don't already know.
For the sake of sanity though it may make sense to have a limit of how many specialities you can learn, say to two. Otherwise you could train any doctor to be a specialist of all three types, and maybe change the rate of learning so higher level doctors will learn more slowly, while juniors can be trained (relatively) quickly.