Actualy Dingo has a resonable idea here.
Personaly I'm tired of running the low level stuff every time I start a new character and would like some way of starting a character at a higher level.
We do it all the time in PnP games the DMG even has rules for starting higher level characters. It allows you to bring a new character in to an existing group near the current level of the party. That way you don't have a 1st level character in a 10th level group.
We already have the shortcut from the noob harbor now; so why not start a character at say level 5 or 6. This wouldn't be a game breaker since it would just allow an existing player to create a new character at a higher level.
Actualy by basing it on a percentage of the XP the character you deleted had would be fair. I would say 30-50% at most or about half the level of the character you just deleted.
The character would start with no money or equipment (so what we all twink anyway) and I would even give them zero favor though I wouldn't be against giving them credit for all the level 1-3 quest on solo/normal if the previous character had at lest done them at that level.
There is nothing game breaking or unbalancing to this since you are deleting a higher level character and starting a new lower level character, of a different class granted and I can see some issues with this, but once again nothing that really breaks the game.
This is something that could be tied to favor or just given as a new perk for the game since to use it you'd have to play enough to have the XP to transfer. Even setting a minimum XP amount so you have to delete at least a level 9 or 10 character before you got this.
Just some random thoughs, but people just because you don't like what someone has said in the past. Think about what he is saying before you get out the matches.