I recently picked up a second-hand copy of Railway Modeller from September 2017 and was pleasantly surprised to see a Narrow Gauge layout built to 10mm = 1 foot running on O Gauge or 32mm track and representing a 3 foot industrial narrow gauge layout. The layout, called A Box & Co (Very) Ltd. was built by Peter Osborne as an example of a Micro Layout. The whole layout can be broken down and stored in 3 standard box files (hence the name - A Box) when not in use.
My own 11mm = 1 foot layout (still to be named) was thought to be unique. Seeing this I'm thinking that there are more 'mad NG modellers' out there working in 'non-standard gauge/scale combinations.