In case anyone is still following this... I've initially gone for the Tamron 24-70 f2.8 and the 85mm f1.8g. The 135 f2 DC and a 50mm f1.4 may follow in time.
I did a lot of research and may as well share my notes here in case they're useful to someone else. Of course the real proof is in the using of them; we'll see how I get on.
It came down to a choice between the Tamron 24-70, or the Nikon 24-120 plus a wide standard prime and wide portrait lens. I've actually gone for the Tamron plus a 85mm f1.8G. I won't bother with a 50mm for now.
It won't be long before I succumb to the 135 DC. If I wasn't tempted by the 135 then I'd probably go for one of the 85mm f1.4 lenses now. I'd also have the 200 like a shot if funds permitted.
My notes:
Standard Zooms
Tamron is not
quite has sharp as the Nikon when zoomed in
Tamron slightly more prone to flare when bright lights included in the frame
Tamron has very slightly more oniony bokeh
Tamron sharper wide open and a tiny bit brighter
Tamron is less heavy
Focusing is about the same
Both have bokeh
way nicer than the Nikon 24-120 and Tamron 28-75 f2.8
The Tamron 24-70 f2.8 performs significantly better than the Tamron 28-75 on full frame.
The old Nikon 35-70 f2.8 is cheap but has no stabilisation, is slow to focus and is prone to flare with off-axis lighting.
Then I looked at
50mm primes too:
1.8D vs 1.8G
Nikon 1.8D is one of the few to go to f22 and is cheapest
The 1.8G has much nicer bokeh than the 1.8D, is faster to focus and is sharper, especially at the edges.
1.4G vs 1.8G
The 1.4G is slow to focus and not very sharp wide open, but generally sharper overall.
The 1.4G is better in the f2-f4 range than the 1.8G
1.4G vs 1.4D
The 1.4G has better bokeh than the 1.4D
The 1.4D is sharper and faster to focus than the 1.4G
1.4D vs 1.8G
At f1.8, the 1.4D has rounder but edgier bokeh, not a lot in it.
At f2.8, the bokeh is very obviously angular on the f1.4
At f4, the 1.8G has much nicer bokeh
Sigma
1.4 is big, sharper at 1.4 than the Nikon 1.4G, better bokeh, slightly worse focusing but actually very similar to the f1.4G
Art variant is way more expensive and way sharper than the non-Art model, bokeh v similar to non-Art variant
The 58mm f1.4 looks very appealing indeed but is most pricey. The 1.8G seems to be the clear winner.
And finally.. I looked at
>85mm portrait primes including
Tamron 90 mm f2.8 (macro)
Tokin 100mm f2.8
Sigma 105 f2.8
Nikkor 105 f2
Sigma 85mm f1.4 (non-art)
Nikkor 85 f1.8G
Nikon 85 f1.4G
Nikon 135 f2 DC
Nikon 200 f2
I made fewer notes at this point but it was very clear that the Nikon 85mm 1.8G is the best value,
(sources include Tony Northrup, DigitalRev, DxoMark, CameraLabs, Matt Granger,
@kman and others)