Progression experience

Hey guys,
I have one suggestion, why not allow players to progress with their char from one expansion to next one TBC>Wotlk>Cata.... ?
For example i raided on wotlk and i want to progress with my death knight to cata, copy of my dk will be made on cata realm and i would be enable to play with my dk on cata, but if i change my mind i would still be able to play wotlk. In that way i don't have anything to lose, in this case char, and i can still try expansion. Since we have huge queue on Icecrown realm maybe some players from icecrown will continue playing on cata and later on mist. I think it would be much more better to have feeling of progression, like you do on retail, then to just start fresh on another server. Since copy will be made, char will probably have to change name, players won't lose their characters and might give newer expansions a chance. Imagine progression from tbc all the way up to mist.
Since realms for cata and mist have lower population this might bring waiting time on icecrown down .

I never worked on WoW but i assume that there is character table in database and copy of just character should not be a big deal, just one more row. Since name must be unique on realm it will probably need to be copied under different name. But what about achievement, items, mounts. If you left them out i would be naked 70 or 80 or 85 lvl char that you can, considering rates, level up in few days, but it won't be your old char with you wanted to progress.

What do you guys think about this idea? Do you agree? What would you change?
Do you like progression or you would like to play on only one expansion?

I think it's a good idea!

I am absolutely for progression experience, so I support your neat idea.
That copy thing.