[Brightcolours]

I don't find it odd: if you mainly take close-up shots, then it makes sense to look at macro lenses instead.
Again, whatever floats your boat.

FOV matters for the outcome. I can take 35mm close ups, or 55mm close ups, or 90mm close ups, or 135mm close ups, and the resulting images will be very different. And if I want longer, like 200mm, 150mm won't cut it. Neither will a widening FOV from focus breathing. 

If you mainly take 200mm close up shots but some other 200mm landscape shots and sometimes go down to 70mm as well, it does not make sense to want to substitute that with 150mm fixed focal length macro.

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Well, ok... let's see how this works in practice, I have doubts, to be honest.

Regarding non-extending lenses, I do disagree with your statement. Moving the inner lens groups moves air around, but only air that is in the lens already. So, in theory, there should not be any dust.

Practice shows: there is. But a lot less than in extending zooms.

I'm siding with BC here:

If the filter is of the "micro particle size" which is common theses days in the like of modern cars vacuum cleaners etc ......... there should be no problem with dust ....... I had been wondering why a filter had not been added before!

  ......... as for the Canon 70-200mm it's another masterstroke optic for sure ...... but it focus breathes and the Sigma 150mm F2.8 macro doesn't ......... (I've just checked)

How exactly did you check?
The non-OS Sigma 150mm f2.8 macro does focus breath (narrowing FOV towards MFD) just like my 70-200mm f4.
The OS version focus breathes as well to the same extent  (both do 1:1 at the same MFD, 38cm).