If you do plan on doing this, and plan on doing so permanently, I want to share some GOOD NEWS:

1) You can still transfer characters from the dead account to your main. Boom, incoming handful of level 80s if you want them.
2) If, like me, you only bought the "Celestial Steed" or other fluff on your main account, once you transfer your alts to that main account it's now available to them. Forever. (I was only transfering to claim an X-52 touring rocket, but BONUS)
3) If you change your mind later and want to go back to multiboxing, you can transfer back and keep the goodies.

That was my experience, and is of course always subject to change according to the ESRB warning.