I believe the above is a wonderful idea, and I would fully support the use of it (and would code it, provided I had the skill needed). This feature would be extremely helpful to those who create another account (either because they want a new username or due to any other number of circumstances), as it would allow them to "transfer" their remaining paid time to their new account. The old account would become a free user, and the new would become a paid account. Or the user could divide the time equally and both accounts would hold a status of "paid".
Let me know if this is under development. I could find nothing in the suggestion area to prove it either way.