I believe the auto spawner takes mob essence to run though. And the way you get that... from a mob grinder around a mob spawner. We also don't use chunk loaders, so they can't just set it up wherever they want to get the essence. They'd have to be around it. We have gregtech installed in an attempt to try and prolong the game and put a little difficulty into it. One thing that can be done with mob spawners... collect a bunch of blaze ones, have your grinders around them, funneling all the blaze rods into furnaces to generate power, which will power the grinders and give you some extra. Free unlimited energy with minimal work. I'm trying to stop stuff like that from happening.
Short story: On my server I have morph. I dont use the flight of bat mode cause I think its a shortcut to MPS flight and the glider/jump assist does me fine. My gf loves flying around, and only really builds stuff in a house she built in creative on the plateau next to me. We arent competing, and I dont mind that shes taken a short cut.
Alternatives:
Chicken coup, vacuum hopper eggs into a dispenser that hatches chickens, grinder to make chickens into mob essence
Cursed earth into mob grinder for mob essence
Essence berries into mob essence via autonomous activator+sewer
(Maybe best) cursed earth in mined out nether fortress chunk to give you wither skeletons, blaze, skellies, magma cubes, pigmen, and anything else your nether might have. Gives coal, witherheads to make netherstars, and blaze rods all usable for power. Chunk loaded using two vanilla hoppers trading a piece of dirt between them.
Point: Maybe its not a big deal that people get energy from blazes. If you're playing GT seriously, blaze spawners are piddly power compared to late game alternatives. All energy in MC is net gain otherwise no one would use it. Sometimes I find I need to relax a little on my personal vision of what the game should be so others play there too. Though it is your server in the end, I am just offering my perspective for what its worth.