Yet another do-it-all (mostly) biek

A post for some thinking out loud; comment/advice welcome. With a big birthday coming up next year, I'm thinking about ordering something custom to replace my venerable Eclipse Countryman ( https://www.lfgss.com/conversations/300040/ ) - much as I love it, there are a couple of things that could potentially be improved. The goal is to have something for fast touring/Audax/day rides (a mix of road, crappy lanes, and bridleways), probably keeping the Eclipse for loaded touring (maybe getting a new front fork with lowrider bosses for it?).

What I like about the Eclipse:
-incredibly comfortable ride
-old-skool aesthetic (yes, this is shallow, but I'm not going to pretend it's not a factor...)

Could be improved:
-slacker ST/longer TT
-slightly larger clearances - I'm a big lad, and like the cushy ride of 35mm tyres (or bigger), but with guards they're at the limit of what the frame will take.

Decisions to be made - I'm aware I have retrogrouchy tendencies, which on the one hand I'm entirely philosophically ok with, but I don't want to be ignoring superior alternatives just because I prefer the old-skool:
-proper bike fit first? This seems sensible; since breaking my collarbone a few years back my position on the bike seems to have changed, and I want to make sure I can still do (slow) centuries in reasonable comfort.
-headset; I'm leaning towards a posh threaded one, on the grounds of ride comfort and weather sealing.
-wheel size; do I want to try and join the cult of Heine and go for cushy 650B? If 700C, then I probably want clearances for at least 37mm with guards. This then leads on to:
-brakes; I'm reasonably happy with my Weinmann centrepulls, so do I again go for the cult of Heine and go for direct-mount centrepulls, whether Weinmann, Mafac, or Compass (£££)? If going for 650B, then AIUI centrepulls limit you to 42mm tyres with guards; does this mean I'm missing out on good 684-47mm tyres (WTB Byways?). Otherwise I guess it's cantis of some kind for rim brakes. Or should I accept the downsides of a stiffer fork and go with discs?
-gearing/controls; I'm happy with my 8-from-9 gearing on a 7-speed freehub. (52-30 chainwheels and a 12-32 cassette), but getting new (or NOS?) components to work with this might be a challenge. I'm not fussed about STIs, so will probably go for DT shifters or bar-ends (or maybe something like Kelly Take-Offs?). I'm also tempted by the simplicity of a Rohloff; I've used Alfines before, but have no experience of the Rohloff.
-Other custom features? Direct mount mudguard fitting (for GB/VO metal guards?); rear triangle pump pegs; braze-ons for dyno wiring/lamps; custom minimalist rear rack for a Carradice?
(Edit - some degree of Rinko capability; QR/split mudguards etc?)

Which builders should I be looking at for this? Current thoughts are Dave Yates (if still building), Varonha, Hallett, Stanforth, Woodrup, Mercian? Sven and Swallow maybe?

This sounds like a nice project, with plenty of scope for creative thought.

The frame builder Tony Oliver was always enthusiastic about braze-on centre pull brakes, he has a discussion in his classic book Touring Bikes. I guess you can add Paul and the Dia-compe/Gran compe to the list of such brakes.

If you are considering Kelly Take-Offs, then you may like to look at Gevenalle brake/shifters and the Dia-compe wing shifters.

You could add an inner front pump peg to allow a Zefal HPX pump to be carried under the top-tube without the need for the usual velcro strap in that position. If the bike is to be for fast touring, then you might want to at least get braze-on mountings for a rear carrier that could be added instead of the saddlebag frame.

Can you get a test ride on a Rohloff-fitted bike? It would be a pity to go through all this planning and then not like it ;-) I'm not sure there are great solutions for gear shifters with Rohloff that fit drop handlebars.

Yes, I'd noticed Tony Oliver was a fan of centrepulls (and indeed of 650B wheels...). I'd not seen those Dia-Compe wing shifters before; very much like the old Suntour command shifters. Not cheap, but then neither are most of the alternatives.

I think I'd prefer the pump in the rear triangle because it allows the bike to be shouldered more easily; helpful when rough-stuffing etc.

It would be sensible to get a Rohloff test ride or two in to see if I like it; I suppose the easiest would be to take a trip to Thorn. For drop bars the best solution would seem to be the Gebla Rohbox.

Have had some discussions with Hallett and Woodrup. Kevin Sayles at Woodrup commented:

At 6' 5" I'm thinking 650b wheels might look 'small' on a frame sized to fit you?... there are more tyre choices available now for 700c wheels, I've recently built a frame to take 700 x 45 tyres, anyhow it's perhaps something you should consider, but of course if you are set on 650b then no problem.... other than I'm informed that obtaining no-disc 650b rims are getting very difficult and that's before the current issues the cycle trade has experienced following Covid etc.

Should I just be looking at a 700C frame with big clearances for cushy tyres, and if so, how big (with room for guards)? What #supple all-road 700c tyres are there? Looks like Marathon supremes come in 40mm, Gravel Kings in 38 and 43mm , Rene Herse in 38 and 44mm.

Ultradynamico in 42mm.