I will probably get jumped on by irate teachers here . . .
Whatever the rights or wrongs of training to be a teacher via an apprenticeship route, I don't think it's helpful to compare average maths graduates salaries with that of teachers.
Surely we all know that maths graduates who move into finance sector roles earn higher than average salaries? This is because of the type of capitalist society we live in where making/managing money is considered to have more value than many "caring" roles.
I myself am an AHP in the NHS, similar training time to teachers. I don't actually think the time taken to train is really relevant. I earn the same as a grade 6 nurse, salary band roughly 26k to 35k. It can take many years to get to the heady heights of 35k and is not guaranteed. New graduates earn early twenties.
It's the same situation across many public sector roles, nursing, teaching, social work, Allied health professionals. We could argue forever, about how these jobs are undervalued and underpaid. However I chose this job knowing the salary possibilities. Surely it is the same for all public sector roles?
I think the salary paid to teachers and similar professions is a wider argument, needed to be considered in a wider societal context.
As to whether teachers can be trained successfully via an apprenticeship scheme, I really don't know. I would echo many of the concerns raised by teachers on this thread. I don't think it's an impossibility but would be most concerned about the impact on existing teachers. I would guess it would have a huge impact on workloads for existing teachers and as previously pointed out with no financial compensation.