Regarding the feat, I would gate it as above (AMPCs/MPCs or coming after the kind of RP that is currently in the feat description and a failed DP check).
As to the more general, we have to do that as a community, but my quick suggestion would be to encourage players to apply for and play AMPCs, including AMPCs that are meant to be of relatively short life spans, rather than necessarily aiming for the full six months.
One idea: Play an AMPC confined to a specific location that "pops up" now and then unexpectedly to turn the routine dungeon run into the terrifying.
Above all, if we want the server to be scary, resist the ever-present temptation to metagame and to flex. If AMPCs are stomped on as soon as they show up, then no one will want to put the thought or effort into playing them. Likewise, though, no one should take on the role of AMPC with the idea of using those powers to stomp on lowbies.
To bring it back to Voracious, the feat should primarily be something horrifying, not something taken for its mechanical value alone or subsequently looked at as the golden opportunity to declare open season on the character. Yes, you see someone eating another human in plain sight, then by all means such revulsion might make you want to strike first and ask questions later. But don't, for example, use OOC knowledge to behave toward that PC in an unnatural way in an attempt to acquire IC knowledge that will allow you to justify killing the PC.