I actually really like this idea. Perhaps even implementing it with the /h command could be interesting.
That's actually a really good idea, as half of players don't even use coords, resulting in help, spotting and marking commands being somewhat reserved for player's who can use coords.
Having a firework shoot up when a player uses a command could be quite good, especially for new player who will see Hunter23 marked POTATO at 49898 388599 +-087, and die of confusion.
I don't think a firework in the players inventory would be necessary, because if they are merely spawned at the players head or whatever, it will travel staight up and go kablooie. Complications may arise, though, when a player uses it indooors or something, because if the firework is modified to noclip through all surfaces, it will cause confusion as the the playeres exact location, and if the fire work is normal, it will hit any roof and explode there, meaning that people who are above or below cannot see the signal.
Another coding obstacle would be the team aspects, as when you /mark or whatever, it only give the coords to your team, but if a regualr firework is shot up, all player can see it, alerting Survivors that their ally in is need of aid, the spotted that they are being watched, and the Hunters, indicating that one of their own is requesting help. This could result in a Hunter spotting a player or a Survivor requesting help, and all players then conering to that location in an all-out bloodbath that will probably end the round fairly quickly afterwards.
If it can be done, it would be cool, though.
/m a enchantment table, bvlue flare go up, request help, red flare. Survivor i =s getting away, /s and yellow flare alerts other Hunters.
It also might help the fact that many players ignore coord listings even if they can use them, which could change gameplay drastically. It could possibly be an optional feature in the input file, although thats even more coding.
Blargh, my brain is tired. I'm going to stop now.