I do this today with my various Google accounts by forwarding one to the other, then using the 'Reply from the same address the message was sent to' setting in

I do this today with my various Google accounts by forwarding one to the other, then using the 'Reply from the same address the message was sent to' setting in the 'send mail as' section in the settings. This way I can have multiple addresses feeding into the one inbox with one contact list and the ability to send mail as anyone.