I really like that Centurion. 

That said, I have a strong preference for indexed shifters for the rear.  Front friction shifting, not a problem for me.  I think you are aware that I have half step plus granny shifting on my Lynskey and Sherpa.  I thought I was the last person on earth that used that, so I of course have to comment on that on the Centurion.

If you ever want to add a third bottle cage on the Centurion, you could put the pump under the top tube.  I did that with my Grand Prix.  I glued some inner tube rubber to the top of the pump handle so that only the rubber presses on the paint, so far no paint damage.  And use a Velcro strap near the front of the top tube to hold the pump in place.  Attached photo.  Disregard the foam pipe insulation on the top tube, if I have to lock my bike to a post I like to have something to prevent paint damage.

...
Last photo shows a tensionable sling saddle I intend for a drasienne (balance bike with Fred Flintstone drive) project I'm doing. A couple years ago, I was able to paddle (not pedal) for 30 miles on a less ideal saddle for the purpose, now thinking I could do more with the sling...no leather treatment needed!
See... https://fr.wikipedia.org/wiki/Draisienne

Best, Dan (...who loves bikes in all forms; saddles, more specifically)

Your saddle sling, good luck with that.  Or should I say, ... yabba dabba doooo.

I have found Sno-Seal to be a valuable adjunct for use on my black saddles. I have not used it on my one Honey Brown model as I don't want it to darken as much as I know it would with Sno-Seal.

Yesbut yesbut yesbut if you put some wax of whatever provenance on your Honey Brooks, she'll get a deeper tan with every application, and when you stop you'll have a custom brown saddle that nobody else has.

Americans have a similar leather wax with a good reputation from vintage times forward, the name of which now escapes me.

Andre, John, there is another option I have used to waterproof leather for 55 years: Sno-Seal.

The tin promises leather protection from rain, snow, salt, sun; the original beeswax waterproofing. Mile warmth helpt it absorb, excess is buffed off with a clean, soft cloth. Instructions say, "Beeswax waterproofing lubricates leather and protects against dryiomg and deterioriation far longer than greases, oils, and animal fats. Sno-Seal is a natural wax and, unlike other products, will never weaken, decay, or break down leather or stitchings and seams. Caution: Will somewhat darken leather; spot test if appearance is important". I have found Sno-Seal to be a valuable adjunct for use on my black saddles. I have not used it on my one Honey Brown model as I don't want it to darken as much as I know it would with Sno-Seal.

See...
https://atsko.com/product/sno-seal-wax-8-oz-jar/
https://www.amazon.com/s?k=sno+seal&channelId=520&clpRedir=Y&plpRedirect=mhFallback

Available from Amazon Canada as well... https://www.amazon.ca/s?k=Sno-Seal&crid=F5Z4IT6ASXZH&sprefix=sno-sea%2Caps%2C363&ref=nb_sb_noss_2 I think it is too pricey due to the added tariffs and would not buy it on principle if I lived outside my borders.

I always treat my Brooks leather saddles first with Proofide (now white cream, I preferred the older red formula that smelled much stronger), then after some use, Sno-Seal for regular winter riding. I lay on a thin coat of Sno-Seal to guard against water drops in between my dismounts and slapping on the saddle cover (I don't ride on the cover per Brooks' caution, as Andre notes). I have found the Sno-Seal polishes out to a high gloss under my cycling shorts, then thins out and needs reapplication in time. It lasts longer in winter when I ride less often. I use it primarily on the Brooks B.17 fitted to my commuter Fixie. I don't use it in summer when I am likely to produce a lot more sweat and a "waterproofed" saddle has much less appeal.

Best, Dan.

Andre, WRT your comment above, Americans have a similar leather wax with a good reputation from vintage times forward, the name of which now escapes me:

You may be thinking of Obenauf's (a company based in Idaho), which makes Leather Oil and a paste. They advertise their products for forestry workers and firefighters.  I used their products for leathers and boots when I was riding motorcycles.  I still have a couple of bottles of Leather Oil, which I've used on my Brooks B17 (now 15 years old) -- an annual end-of-season wipe with a Leather-Oily-rag seems to work a treat.  (Mind you, anytime I'm riding in wet weather, I use a cover for my saddle.)

'Cos of The Situation, I won't be buying any more any time soon, but Mike, you may find it useful.

Just now appearing on a literary group I run, notice of a biography of war hero and legendary bike builder Jim Wilson in the Sheffield Star:
https://www.facebook.com/groups/indieauthorsinternational/permalink/29028059490166265/

"He Hath Courage"  World War 2 Hero and Legendary Sheffield bike and frame builder who 'lived the life of 10 men'

Check out the photo of him wearing a military woolly pully and a tie while working on a frame, VOSC (Very Old School Craftsman).