Thanks for the interesting read.
I would be interested in hearing how you maintain the actual icons themselves when not using a 3rd party icon set. Would you create these in a seperate document and re-export an iconfont every time you have a new icon/updates? I currently keep my icons in the Symbols page (and have 3–4 different color variations of each), but It’s super annoying to export to iconfont since I have 300+ symbols and only need 30 for my iconfont (and the artboards are not next to each other in the layers list — cause I have them next to the same symbols in different colors). And It quickly becomes messy to have the black icons outlined (for iconfont svg export) and keep another version stroked (in case I need to modify the icons/thickness).