Dr Gerard Bulger:
Direct Exit to a different IP.
I naively thought that the proxy lines in torrc could to that via an https proxy. Alas that's not what that line is for!
I got an impression from earlier chats a while ago that exiting to a non-advertised IP was regarded as simply not cricket, in that the internet should know the IP or Tor exits exiting. The trouble now is too many are sites apply blanket bans on Tor exits.
Starting with tor 0.3.0.x if your exit relay has multiple public IP addresses you can use one of them for exiting only without the need of an additional VPN (which degrades performance), but keep in mind that this not-announced exiting IP address will also be listed in the list of exit addresses. https://collector.torproject.org/recent/exit-lists/
I'm not sure how much difference it makes depending on your exit relay bandwidth (smaller exits will likely benefit more from it).
https://www.torproject.org/docs/tor-manual.html.en#OutboundBindAddressExit ansible-relayor even supports automating this.