I think it depends on the origin of the teacher, and their quality, rather than the subject being covered.
So given a stable of good teachers I would say that History, Geography, RE could probably be taught, in Y7, by a teacher of any of the others.
Pretty much any DT subject by a teacher of any of the others. Art / Textiles also probably interchangeable.
English teacher teaching Drama - probably OK.
Any Science teacher could teach Science, whatever their subject specialism.
Maths teachers could also possibly teach the Physics element of science, and a strong Physics graduate could probably also teach Maths.
A PE teacher with an A-level in Biology could also probably teach Biology, especially the human aspects.
An MFL teacher with a specialism in 1 language but an A-level or higher in another could teach their alternate language.
However, even though I feel that one Humanity could be covered by another humanity's teachers, it doesn't follow that e.g. a PE teacher could teach history, or an Art teacher RE. It matters what the background of the teacher is, as well as the subject they are required to teach.