(yes, 5 years later...) Excellent responses already! I've been considering/researching this question myself, so will contribute what I can. I am also a bit of a novice with a steep learning curve, so take my responses with a grain of salt.
would recording via the desk (utilising pre-amps, sends to rack
effects etc), and then bussing to my audio interface and then mixing
in Logic really bring anything to the sound (in terms of the 'warm'
and 'colour' that analogue brings)?
That's purely on you to try it out and see if you like, appreciate or find use for the sort of coloration the desk imparts. Even falling apart equipment is often used deliberately for effect. The first garage bands deliberately slashed their speakers for distortion! Some award winning photographers deliberately use crappy cameras/film as part of their artistic vision. So it really depends on what you want vs what the equipment can provide. There is a use for everything, though, albeit it might be creative or less conventional.
Would the post-desk processed analogue signal be stripped of its
'analog warmth' if it's transferred to Logic for mixing?
No, as long as your bit depth, sample rate, S/N ratio and A/D Conversion are of sufficient transparency, they should accurately retain whatever sounds you hear UNLESS those sounds are ONLY expressed in the monitor outs signal path for some reason (in which case, you might creatively use THAT signal pathway as your out to the A/D Converter). however since you are imparting this sonic footprint at the beginning of your signal chain, you need be careful not to lose it in too heavy-handed processing in the box. Your goal from that point would be to subtly enhance, bring forth and steward that sound, rather than distort or bury it (unless that's a specific effect you're going for). Again, it's entirely up to you.
Additionally, if I do invest in an 8-track recorder (trying to
currently locate a cheap working Fostex A8), are there any recording
configurations that would 'add' to the sound overall? The best I've
come up with is Signal > Desk > mixed and processed to 8-track tape >
8-track tape recorder to Logic (via interface) for mastering - or is
this just taking a longer route that will ultimately reach the same
The tape and machine will most certain impart a flavor, especially if it's not in great shape. Whether it's something you want to add to the sound of the desk is up to you. I feel like the others did a great job of warning you of the potential of getting in over your head, depending on your expectations. But again, some people like the sound of a deteriorating tape deck. It's just a question of how much money, time, space, etc it's worth to you. The Digitech Obscura Delay pedal was created specifically to model the sound of a deteriorating tape echo/delay. You could add that sound in "more authentically" and "manually" if you wanted.
But that brings me to my final point: For me, personally, I am not looking to add "analog warmth" to my recordings so much as construct an "analog-style workflow" (with any mix of analog and digital equipment) for myself to learn the tactile fundamentals of analog mixing. For me, it's an educational process in that every DAW is some level of metaphor, analogy or abstraction from the analog recording and mixing process. I want a firm grasp on those fundamentals of signal chain routing and workflow and ear (vs eye) training, and a focused and, yes, an artistically-limited workflow before I engage too deeply with the abstract vagaries and complexities of a full-featured computer-based DAW and mixing in the box with a mouse and keyboard across screens and menus and abstract interfaces. I don't want to use that (imaginative/abstract) part of my brain for logistical purposes while I'm recording and mixing. I want to use it for creative purposes while I intuitively grab and tweak physical knobs, push physical buttons, and slide physical faders on a complete "What you see is what you get" physical interface in front of me with no hidden options or menus. So the psychological and pedagogical aspects of an analog workflow I think are certainly worth considering as "adding something" to the recording!
There is a risk of romanticizing analog, and I had to check myself to see if that's what I'm doing. I'm looking at a VERY simple 2 in, 4 out multi-track signal chain, where I am only mixing UP TO 2 mono or 1 stereo signal at a time in context of the rest of the recording (either individual mono/stereo tracks or/then mono/stereo stems and finally the stereo master), hopefully with some parallel processing. For me, the benefits of the limitations and reliability of a computerless system outweight the drawbacks of only having one type of compressor, one type of EQ, manual automation -- at least right now. Once I feel more experienced, I'm sure my perspective will evolve.
How I imagine that process will look for me is a multi-track recorder/mixer hooked up to something like a 6-slot 500-series module bay that has a stereo mid-side processor (IGS Bison) feeding a compressor/limiter (dbx 560a) and parametric EQ (dbx 530) x 2. (so Bison > compressor > EQ > compressor > EQ). This will give me some mid-side mix processing, the ability to mix stereo in parallel, and also the ability to sandwich compression with EQ or EQ with compression for mono tracks that really need it.
So hopefully it will remain pretty focused, compact, manageable, and give me good experience of learning the fundamentals, and I can take that knowledge and experience with me into the transition to a full DAW with a nice analog-style control surface.
(Yes, this is still on-topic, I swear!) To me, this is analogous to a composition workflow valuing the importance of abstaining from notating anything, for example, until the idea is really well developed and clear in your head. If you go to notation too quickly, you engage the wrong part of your brain and lose the creative thread. I've felt that sort of thing happen to me when I've "gone into the DAW" with too little analog-style recording and mixing experience.
So, apart from the sonic possibilities of imparting an "analog sound" to a recording, I think one of the greatest real-world uses of analog mixing combined with digital recording is psychological and pedagogical for those of us (me) who have a lot to learn about the fundamentals.
At the end of the day, it's great you're being thoughtful about it and not just doing it for the of doing it or for the "idea of it." Because of that, you'll figure out when, where and how to integrate analog equipment into your workflow and signal chain.