Well I'm going to be real sad when this 420 goes. I was able to pick up some 700x32 Panaracer T-Servs for a good deal--black wall--and they look great on the bike. Super cheery color meets a ton of black, with those tires helping give a rough-and-tumble vibe to the whole bike. I dig it. The tires (folding bead) are also considerably more comfortable than the 25mm Vittorias. And while the bike's willingness to rock back and forth out of the saddle is even less now (than it was with the 25s), it is even more dead-nuts stable. Sure, its 25.6 lbs (11.63 kg) helps keep things rubber side down, but with the 32s, there is an in-sync solidity between frame and componentry in completing the bike. This is simply a great bike to ride. It even, to my preferences, turns markedly better than both my 620 and 720. This is primarily noted with initial turn in at medium to slow speeds--it doesn't "fall" like the 620 or feel a little lighter perhaps like the 720. While the other two tourers sit between 53-56mm of trail, this is at 59mm, which I think plays a part.
So my daydream-level plans for this, which I had kept to mostly myself should the bike be "worthy" (in a sense) via its on-road character, has been 650B with fenders. It has the clearance, it has great on-road characteristics, I have tires for it, and I would be happy to build wheels for it. And like probably I've mentioned elsewhere, the levity of the yellow paint combined with the very low buy-in price just make it really 'accessible' mentally, with a fun and "what do you have to lose?" element very much present. As is, this is just simply, a great bike. Great gear range, proven components, dirt cheap consumables, extremely comfortable STI shifter levers, etc. And as an aside, if one is looking to run STIs on their vintage groupset, say an 8-speed 6400 setup, knowing what I know, I'd run the Claris levers and not think twice. The rest of the 6400 groupset will be lighter (than the Claris components), but the ergonomics (regardless of bar shape or mount location) of these current-era Shimano STI levers is top notch, IMO. Add in the dark grey of the Claris levers being pretty close to 6400's grey, and to me it's a no-brainer.