I don't see the point to this event if the rare spawn rate has been cut back to default levels. This event is going to reward people who, for whatever reason, already have a lot of lanterns, rather than reward people for going out and hunting them down during the event.
Here's how impossible it is at the moment:
The most efficient method of finding Hallo Rappies is running VR Temple on Normal, encountering the first 7 rappies, and then remaking the game.
Doing this as quickly as a player can, the best case scenario is one run every 2 and 1/2 minutes.
Under default rare spawn, each rappy has a 1 in 512 chance of being a hallo rappy. Since under ideal conditions you encounter 7 rappies in a run, an ideal run has about a 1 in 73 chance of giving you a hallo rappy. This means you would need to do an average of 730 runs to get ten jackolanterns, assuming every hallo rappy you find drops one (we have seen them not drop them before.)
So, an average of 730 runs to get 10 jack-o-lanterns. At an average of 2 minutes 30 seconds per run, a player could fit 24 runs into an hour. This means that even if a player did lantern runs non-stop during the entire 24 hour period that the mini-event is going on (~576 runs possible) they will not get 10 lanterns. A player who played for any reasonable amount of time couldn't even expect to see a third of the lanterns necessary to trade for a mag.
This event will only reward people who already had a significant stack of lanterns before the event began.