Chromis would not work, at least not normal ones. Im looking at having either a white mouth, golden tail, skeletor, or possibly even a Dragon moray eel. So really anything 3" or less is ruled out. Also I might have a chance at getting a Mombasa lion which is would eat anything less than 3" for sure. Any thoughts?
The goldentail eel & skeletor eel would probably not pose any threat to the chromis if you keep them decently well-fed; people have kept them with clownfishes without any issues after all. The white mouth eel & dragon moray eel will outgrow that aquarium as it really comes down to the thickness vs. length of the eel for what you can fit in any given aquarium.
IMO, you should just skip the whole schooling fish part if you want to focus on predators & such as you're seeming to indicate (eel, trigger, lionfish, etc.) as you're going to be pretty overstocked in no time at all.