Recall Boston being relegated/demoted two divisions from the 4th tier (EFL) to the 6th tier (2nd step of non-lge) in 2007 (maybe 2008) and this ultimately saved Alty from relegation from the Conference (step1 non lge)...
That was a strange period when we finished in relegation zone 3yrs running between 2006-2008 (i think) and we were saved from relegation by financial issues at other clubs like Halifax, Boston, Canvey Island, Scarborough, etc.
During that period we also had the 'James Robinson' issue of fielding an ineligible player (though at time harsh as unaware) that cost us 18pts but again we had a reprieve as one of three seasons listed above...
Agree that demotion two divisions for Grimsby & Southend would be funny but would also send strong message to EFL clubs (who all know rules at start of season) not to try to override/beat an agreed system that rewards via promotion & has relegation for failure...
Bottom line is over whole season Southend & Grimsby were the worst teams in their division & thus deserve (under the rules) to be relegated... they should stop moaning because they were crap and if they continue demote them two divisions as extra punishment!