I'm not familiar with RIPPLE gateways, but my guess is that they will need a new set of open ports and connections to another network. To me that looks a bit risky in terms of security. Can you elaborate a bit how they work?
Its well documented, its older than Bitcoin. https://ripple.com/wiki/How_to_Build_a_Gateway#Building_a_Gateway
Mustn't necessarily run on the same VM, but could be bound to a MN, or better a registry of MNs.
The registry would auction the issued IOUs.
The earnings of the MNs could be payed out as a dividend on your issued IOUs.
The coins could be locked for spending, if there are IOUs issued against them.
It would be great at all if there were a Ripple gateway for DRK.
The system has a lot going for it at the moment.
The Ripple coin is another story, the recent rise is due to an amazing news headline.