I wouldn't delete a level 70 character (or one at 68 - just to roll a new toon of the same class to dual box. (multiboxing is addictive and you will suddenly want to 5 box and have a tank )

Either transfer one of your 70's over to the other account (downside is it costs, but it did cost you more to level it) or you could delete the deathknight name you reserved and instantly reserve it again on another character on the second account. (make sure you have all the details ready to go so you can register it as soon as the original character is deleted).


This will free up a space and allow you to keep the name reserved.

Class wise - any two ranged classes of the same type will be doable. Roll a few combos and see which you prefer playing.

** EDITED TO FIX SOME TYPOS **