Andrew, welcome. In some ways we're in similar places with our Df experience, in some ways not. I'm coming from m43 and APS mirrorless, not Leica, so probably different expectations that way. I am something of a prime lens fanatic but not really a bokeh fanatic, so different priorities there. And the "middle" focal lengths have just never worked for me, or me them, or whatever, so I have a cheap 50mm f1.8D (which I like as well as I'll ever like something in that range and paid about $75 for) and the 58 f1.4 is not on my radar.
BUT...
I tend to shoot a LOT of wide angle and a fair amount of short (portrait length) telephoto, so I'm in your same ballpark on some of the other stuff. I too have the 24mm f2.8D and the 28mm f1.8, both of which I like a lot. I don't have a 35 for the Nikon because I have a Sony RX1 which I sometimes take out with the Nikon as a 35mm option and often take out by itself when I want to travel light. That Zeiss 35 f2.0 is nicer than any Nikon I'll ever buy and I like having that higher-res, higher DR sensor for some shooting too, so that's my 35mm. I have a 20mm f2.8 D also that I really DON'T like and this is one of my favorite focal lengths - as wide as you can go without getting into ultra-wide angles and distortion effects, so I'm in transition at that length. I bought a used Zeiss 21mm f2.8 which was absolutely fantastic. I could handle it but it was a bit larger and heavier than I wanted as an everyday walk around lens, but I was gonna keep it. And then I was still within the return period when Nikon announced their new 20mm f1.8, which has gotten excellent early reviews and is similar to the 28mm f1.8 in size and weight. So I reluctantly returned the Zeiss 21 (which was one of the more difficult things I've done, although I'm saving a boatload of money) and ordered the Nikon 20 f1.8. I'm hoping it will be similar in quality to the Fuji 14mm, which was my favorite Fuji lens and the only real regret I had when I sold my Fuji gear and moved over to the Df...
The portrait length is more of a challenge. I have an 85 f1.8 D which I like well enough to cover the shorter portrait length. But I want something in the 120-150 range also (I had the amazing Olympus 75mm f1.8 with my m43 kit and LOVED shooting with that lens at that 150mm focal length) and that's a tougher nut to crack with this system. I too have the 24-120 f4 zoom which actually handles that 90-120mm range pretty well for my uses - you don't get the extremely narrow DOF or low light capability you'd get with the 105 or 135 DC lenses, but with the Df's low light capability and the VR in that lens, it actually does better for this type of use than I have any right to expect. So that'll hold me as an AF lens in that range for now. For 135, I had the same reaction to the f2.0 DC lens that you had, so I'm holding out. In addition to it's size and weight, it doesn't have VR and at this focal length, I think that can start to really matter, particularly for low light shooting. There have been persistent rumors that Sigma is getting ready to release a 135mm AF/VR (or whatever Sigma calls VR) at about f1.8 or f2.0, but still no word on that one. So to hold me over, I went on ebay and found an excellent 135 f2.8 AI lens for $150. It's actually a great old lens and I was lucky to get one in pretty much perfect condition. It's manual focus and no VR so I don't know that this'll ever be a primary lens for family get-togethers in lower light, but I'm gonna give it a try this holiday season (along with the 85 and 24-120) just to see how I'm doing with this gear. I might even rent a 135 DC to see - maybe I'll like it more than I expect I would??? The other option might honestly be to find a used Olympus m43 body and 75mm and just keep that around the house for those uses - I tend not to travel with that focal length anyway. Then again, if I rent and end up liking the 135 DC, I could treat that the same way and not worry much about the size/weight. We'll see - I don't have any idea how that one's gonna shake out... Here's a pic of the 135 f2.8 AI on the Df - there's an f2.0 version as well, but it's bigger, heavier, and a lot more expensive (although still around $400-600, so not wildly expensive), but this little gem will hold me for a while...
135 tests-1 by
ramboorider1, on Flickr
I actually like the 24-120 zoom a lot more than I thought I would, given my general aversion to zooms. I could conceivably see using it as a travel lens. I don't mind carrying it as long as I'm not carrying much else. Maybe that and the 20mm and one faster prime (28 probably or the RX1) for low light... I don't like most zooms because the typical 24-70/80 doesn't give me much I use other than my typical wide 24.28, which I'm happier shooting with primes anyway. But with the range out to 120, I find that zoom actually covers almost anything I'd shoot on a day to day basis, other than the wider stuff I'd bring the 20mm along for... I'd probably be just as happy with the 20, 28, RX1, and 135 though, and that would be a lighter camera if a roughly similar weight in the bag...
Anyway, the journey continues. Trying to keep it as small and light as possible given the quality and size of the sensor in this great little DSLR...
Looking forward to see how you progress with this system as well, and maybe glean some ideas...
-Ray