One could manipulate the Alliance Dialog with Frame natives.
The whole "AllianceDialog" itself could be scaled down to a almost unseeable thing.
BlzFrameSetScale(BlzGetFrameByName("AllianceDialog", 0), 0.0001)
You could hide the names inside Alliance Dialog.
you would have to call that with index 0 to 23
BlzFrameSetVisible(BlzGetFrameByName("PlayerNameLabel", index), false)
You could scale down the "AllianceSlot" 0 to 23
BlzFrameSetScale(BlzGetFrameByName("AllianceSlot", index), 0.0001)