I understand and respect all the arguments against multiboxing, but please hear me out.
My interest in playing vanilla wow is to get into the nooks and crannies of the content that I've never experienced before. While there are many awesome people on this server, many in the leveling stage are unreliable (or uninterested in the content I want to do).
In the past I've leveled up a Warrior, Paladin, 3x Mage party on a 12x vanilla server, but the server was meh (and 12x). What I'd really like to do is level a full party in a 1x environment with the quality of development shown by Nostalrius. Controlling a full party of 5 with tank, heals and dps isn't that difficult, but it does add an element of complexity to the game which I find quite fun. You can even set up a group such that almost any gear dropped is useful.
Multiboxing allows me to experience the content I want, at the pace I want, when I want.
There must be some way to implement it without creating an unfair advantage. Short of creating a PVE multiboxing server, is there some way to tweak permissions such that people like me could multibox on the PVE server without being able to use the mailbox, auction house or enter raids? Something like a subforum where I could register my party? I suppose there is still the issue of trading, can you limit that to certain players (the registered party)? I've no real coding/development experience so I don't really know what is possible on your end without adding too much complexity.