Is it possible to backdate the appointment of 2nd Director & to backdate adding them to payroll to utilise pa for 2009/10.
I don't know too much about company law, so I can't give a "definite" comment on the retrospective appointment of a director. But I suspect that without a Board Meeting and contemporaneuous minutes you may be on dodgy ground.
PAYE has to be accounted for at the "earliest date", being date of payment, date of entitlement or date that money was made available (for instance in a director's loan account). If none of those dates was within 2009-10 then no PAYE would be due. I know that the situation is a little different in that you are proposing to make a payment at or just below the threshold, but surely a broadly similar principle applies?
I cannot see that you can do something now, deeming it to have happened a month or a year ago to gain an advantage. Income cannot generally be moved backwards or forwards at will.