Apart from the unbalance i think a new player will be overwhelmed by the amount of knowledge which is needed to play rated PvP.
Some one who queues arena since BC will faceroll to 2k in green gear, with any spec, without knowing how to play it.
Even with the knowledge available a new player wont have the interface set up.
Rated PvP is absolutely new player unfriendly. Thats why blitz is appealing, its easier to get into.
I rarely met a PvE healer who uses keybinds for target swapping or party macros. They all click or use mouseover macros/addons.
Show an AWC game to a new player. They dont understand who is winning and why. Try to explain the typical “The guy is toast in the next go” to a new player. The game does not indicate anything whats going on. Thats why we have spaceship UIs.