I’m not sure I follow what you want to accomplish:
a) Send one campaign one time to ~15,000 recipients and get a copy of all ~15,000 messages where the only difference is the per-recipient customization.
b) Send multiple campaigns one time and get one copy of each campaign.
In the case of a) I’m not sure Gmail (or any other receiving system) wouldn’t choke – by design or by default – on a sudden influx of that many messages that almost identically match each other.
In the case of b), just add the “BCC” address as a regular subscriber. This is how I handled archiving all of my newsletters (one copy of each campaign) to Evernote, I added my send-to-Evernote email address as a subscriber.