Major seriously considered resigning after Black Wednesday but decided against it, if he had then like Eden after Suez, the blame would have stuck to him, Lamont would have had to go to in those circumstances, no real loss.
The problem then is you are going to cause an almighty fight for the Leadership, Hurd would probably have been too associated with the ERM policy so he's out. The obvious candidates are Heseltine and Clarke but their views on Europe are way out of line with the views of the Parliamentary Party on Europe, never mind those of the rank and file, had either of them become Tory Leader, with the Maastricht Treaty still to be ratified then the Party could have split. The only possible compromise candidate, one who has been discussed on here before, is Malcolm Rifkind but this may have been before he really came to prominence.
Major had many faults, but rather like Michael Foot a decade earlier, he was just about the only Leader who could have held the Party together.