Websites aside, is it theoretically possible for the bitcoin-qt client to support some kind of 2nd factor authentication?

If not, is it true that OP would still have his coins if his locked payout address was really located at an online wallet behind 2-factor or the address of a paper wallet?

I made a post related to this about necessary security features that
every online bitcoin website should use: https://bitcointalk.org/index.php?topic=294896.0