> The forms already allow you to have a different tax year, though few people make use of that (I have no idea what qualifies people to have a different fiscal year, it might just be for companies, I don't know)

It's mostly for businesses (which includes individual tax payers as sole proprietorships), and the things looked to for non-automatic approvals are things like what your actual cycle of business is like. (For individual tax payers, the only automatically allowed changes are, IIRC, change back to a calendar year as tax yesr and changes to align with a spouses tax year with certain conditions.)