Following advice from the responses, I decided to email the StackExchange team.
The reply I received not only addressed the specific prank that I proposed but also explained the nature of pranks and thus, the guidelines that proposed pranks should be followed. Since I was unable to easily find these guidelines in the FAQ (or other similar pages), I figured it would be useful to post the guidelines here. This way, other users who would like to propose pranks can review the guidelines, thus reducing the email load on the SE team just a little.
Following are excerpts from the email I received in reply to my proposal (edited to exclude the exact nature of the prank I proposed):
When we plan these things, we have some goals in mind:
- The vast majority of folks that see the joke should realize that we can't possibly be serious
- Ideally, the joke doesn't generate a lot of additional support overhead
- The joke causes people to participate in various positive ways
If we do pretty much anything with reputation, we kind of miss the
first two points - the system is very confusing to new users as it is
and a joke feature such as this could end up in quite a few being even
more confused, or perhaps soured on the idea of participating
altogether. A substantial amount of traffic comes from new users
finding the site for the first time.
PS: I originally had this information posted under a different question, but merged it with this one at the suggestion of a diamond-mod.