Custom 650b Bike Input?

[brewsmith]

Looking to get a 650b bike built for commuting/light touring etc. Right now, these are the general ideas I have kicking around:

- compatible with 1x12 force AXS, but also able to switch to single speed for training/cruising.
- 650b rim brake, hopefully clearance for 47mms
- Direct mount paul racer center pulls (this would require a fork build I assume, so is that something you are willing/able to do?)
- Modular rear dropouts for single speed/fixed or QR
- Stay splitter for belt drive (want not need)
- Provisions for fenders and small rear rack

It has been suggested that I consider disc brakes for this build to avoid the custom fork route and simplifing single speed option and tensioning the chain/belt. I have disc brakes on my Bingham and they stop well, but have always had trouble getting caliper alignment just right etc. compared to rim brakes. This may just be something I need to get over, and I have considered going with cable or hybrid disc calipers to eliminate the hydraulic component.

I was also originally thinking aluminum for this build, mostly just because I do not have an AL bike, but now I am back to considering steel....thoughts?

Anyways, just figured I'd throw it out there to get feedback from anyone who has made similar design choices etc.