HD account will use a new address every time you want to receive a payment or send a transaction with change.
We can still choose an address in our wallet to send change like we do now, right?
We are considering maybe supporting multiple outputs transaction in some kind of a plugin.
Didn't get the plugin part. Anyway, ETA?
IMHO a "+" button for adding output addresses is better. See brainwallet.github.io/#tx or 'Blockchain.info custom send' pages.