Well, parliament would have to vote for that... And whilst the Tory back benches may be a bunch of selfish, money grubbing weasels they aren't insane.
The reason the Army answers to the head of state is to prevent this sort of thing.
…the 1922 Committee will have change their rules to have another no confidence vote. I can see them doing this. At the moment it takes ‘x amount of letters to initiate the process but that can only occur once in 12 months’. I can see that changing, a significant increase in the number of letters within 12 months could trigger another vote.