What I have Learned

Okay, I have not built anything yet but here are some observations:

Although the path is longer it was good to start with what can be cut with a laser cutter (2D) and then regroup the layers for a CNC milling (2.5D). Keeping both options open gives flexibility.
I would question building an open races when similar dimension roller bearings are available of a very reasonable price?
It it probably easier to match the bearing thickness to the sheet thickness than not.
In my designs I have both dowel (i.e. 1.25 mm diameter nails) alignment and bolt alignment. If the layers are glued, then the dowels can be removed).
Permanent dowels and split dowels are an option where disassemble is not required.
For wood (MDF) PVA glue is fine, for acrylic #16 acrylic glue is fine (but use safety precautions as it contains very nasty chemicals (methyl chloride)).
Full thread bolts are available in lengths up to about 80 mm and studs even longer. I am no longer relying on the bolts for alignment.
Not hard to design steps to use allow the use of shorter bolts or the use a mix of bolts, glued lamination and permanent dowels.
There is a trade off between thicker sheets and manufacturing. It is not easy to cut thick sheets (i.e. greater than 12 mm). It may be better to laminate (glue) sheets (i.e. 6 mm) for thicker sheets.
The size of my CNC machine limit the size of my project.
Although expensive, commercial laser cutting services can cut pieces beyond the size limits of my CNC machine.

Some slew ring design concepts using roller bearings.

Double open race #1: