Half a stack would still allow 32 to be spawned at once essentially, 1 of each per day would probably be the safest for this idea... As it is, it is more safe to allow only a few SuperOPs to occasionally spawn in animals. In the past, just having friendly mobs activated would lag out the server completely. As Ash said, there are a few farms around you can ask to use when a SuperOP with mob spawning abilities isn't online, but when they are, you may ask for a few mobs to be spawned yourself, and then they can be bred (it is advised not to breed more than 10 of the same mob, to reduce lag).
This hopefully keeps in touch with the natural, legitemate side of the server; we do not want it to be too easy to obtain these items just from spawning millions of them, but the old mob spawners, and even superops being able to spawn however are to compensate for the low natural spawn rates of mobs in main world. If we could fix the mob spawners up better, that would probably be a better solution, being able to gather materials in one area, where it should be contained and easy to clear out... but as it is, I don't think allowing players to kit spawning eggs is such a good idea.
This hopefully keeps in touch with the natural, legitemate side of the server; we do not want it to be too easy to obtain these items just from spawning millions of them, but the old mob spawners, and even superops being able to spawn however are to compensate for the low natural spawn rates of mobs in main world. If we could fix the mob spawners up better, that would probably be a better solution, being able to gather materials in one area, where it should be contained and easy to clear out... but as it is, I don't think allowing players to kit spawning eggs is such a good idea.