Current Projects chat and miscellany

Hi folks,
I'm thinking about asking for a custom frame. First some hints about what I currently ride:

• Bike n°1, Salsa "Madeleine" Vaya. The do-it-all bike, daily, tourer. Handle like a truck, heavy, wheels are also a bit heavy especially with Marathon+, disc brakes are appreciable although I feel the BB7 do not give their full braking potential. I like to carry everything front : two panniers, one giant rackbag or a small handlebar bag on klickfix. Can't go without at least a handlebar bag. I feel that without anything front, the bike could be very lively and fun to ride.
  
  
  

• Bike n°2, CBT Italia. The light bike. As I usually ride on the n°1, I absolutely FLY when I ride n°2. Use the 52T ring without problem. Long rides without being tired. The skinny tyres are a little bit uncomfortable on rough roads. This one should not be ridden with the handlebar bag as it removes all its liveliness (but I use one !) Concerning braking I should say that campa levers + mavic brakes + machined alu rim = OOOMPH! Doesn't not have a permanent lightning system, nor any mudguards.
  
  

Both are steel bikes; I didn't like the ride on my past alu bikes. Titanium is for flying things (kidding).

What to do when you want a bike that is light, fast, with the FLY feeling, confortable on rough roads (not necessarly "gravel", let's say the typical french/scottish/irish small country roads + towpaths ), lively while having a handlebar bag. From what I read on The Internet, I feel I could go with the following:

• fat slick supple tyres. If I don't want heavy wheels, I may want to go 650b. Let's say 650x42b
  
• "low trail" front geometry, as it should result in good handling properties even with a small rack and a handlebar bag.
  
  

Let's add:

• light tubing : this bike should carry too much things and should be, say, under 11 kg all equiped ?
  
• Mudguards, permanent lightning system (dynamo hub, front and rear lights)
  
  

Concerning braking, I have an existential question : Going with discs asks for a beefier fork and probably chain and rear stays. Will it entirely spoil the weight of the bike ? Basically will going for discs necessarly result in a bike that is as strong and heavy as my Salsa, especially I want a steel custom fork ? On the other hand, with fat tyres, the possibilities are either cantilever or centerpull brake (framemounted). I have bad memories of adjusting cantilevers so centerpull would be the choice if I choose rim brake. Koolstop pads make for satisfying braking with Mafac Racer. I guess Paul or Compass centerpulls should be even better.
@edscoble, you ride this kind of bike with both rim and disc brakes, how are your Oak and Elephant NFE in term of weight ? Do the two feel the same with similar tyres ? How is the Elephant on the road ? (I know that it is made for carrying a lot of things, by the way) @psee maybe has a similar experience ?

Any comments everyone ? Thanks for reading !