I didnt had time to read the whole thread, but I might have some tipps for your initial question. In my studio I have among others the DFAM as well as five other semimodulars, a large doepfer rig and all the elektron stuff.
So the DFAM fits very well to the Mother 32, because there you get a MIDI-Interface, an LFO and a small mixer tool, that broadens the possibilities – and its much cheaper than buying all this in modular gear. Buying another Moog Case with 60 hp looks nice, but will come quite expensive (and 60p will become quickly become to small). If you plan to expand the dfam with other modular gear, Id recommend to get a bigger case: a cheap and light TipTop Audio Mantis will do the trick, or get sturdy 9P case from Doepfer.
you can plan your system on modulargrid.net (login with a free account)
If you want to extend the DFAM with modular gear, I would suggest to get an Expert Sleepers FH-2 (8 HP + 4 hp for the din midi extender) first as a midi interface. With this you can play the dfam with any MIDI or software-sequencer. even with an iphone if you wish to.
You will also appreciate an I/O-Module to connect Speakers and a Headphone on the front, the Befaco Out V3 does this and only uses 4HP. For FX and other functions stuff to play around, the expert sleepers Disting mk4 is also a no brainer with only 4 HP.
So these 3 modules will cost you a little over 600 bucks and use 20 hp. Plus the case (300 to 500 bucks)
then you can expand on this basis. A Make Noise Maths serves as a mixer, lfo, attenuator, Envelope generator etc. and is a very popular swiss army knive (20 HP, 300 bucks)
if you wanna spice up the sound with some extreme VCO, take a look at the Noise Engineering Basimilus Iteritas Alter (12 HP, 250 bucks). To mix this with the DFAM and have some dynamic control, a Make Noise Optomix comes in handy (8 HP, around 200 bucks)
So you see, it gets quickly large and expensive. just one full 84 HP row in a modular rig can cost 2000 bucks, and often these systems have three to five rows in the end.
You can also go another route: Buy a Digitakt and let the DFAM just function as a source for Drum & Bass Samples. This combination offers lots of fun and sound design possibilities for a relatively small package and price. If you already have a digitakt, why not combine it with a digitone ? this is a killer combination in my opinion.
Also check out the free Software VCV Rack: There you can test and patch different type of Software modules.