And I've been crew for 6.5 years, before which I ran a leisure travel division within a business travel agency in Aberdeen and had a team of staff (albeit a small one) beneath me. So half a year stands in my way of applying for CSM.
(or more accurately 18 months, because the 12 months needs to have happened within the last 6 years)
But again, I am happy where I am so this is largely hypothetical.
EDIT : re-reading what you've posted above, those requirements are EXTRMEELY restrictive. Basically, I suspect the only people likely to have a shot will be either existing SCCMs with BA or former managers from Atrium Court in Glasgow.
Most other ground managers from BA, either serving or re-deployed to be crew, will be lacking the 36+ months experience as crew. The Glasgow, Edinburgh, Aberdeen or Manchester ground staff, for example, who are now flying, may well have the management experience but are only up to about 24 months of flying experience.