Don’t over look the NEOS insulated overshoes. They can be walked in and I’ve used them with uninsulated hikers inside to below -20F
Those look REALLY interesting. I'm thinking add a liner to the over shoe itself and be done with it.
The W. Mountaineering and NEOS are out of stock but I'll likely buy 1 of each and keep the one that fits the need the best.
Keep the ideas coming!