What do you guys think about it?
8 x 2 = 16 small to tiny fish, most of which like a good amount of vegetation, in a 55 ? It will/would be a tank you have to sit there and study for a while to find most of the fish. You could add to the fish load considerably. (In high school a buddy had a home-made tank probably a bit bigger than a 55, and we put 400 Heter in it. The "gold" ones. Always liked Heters.)
My impression, and I can't give you a good reason for this, it's just my impression, is that L goodei (bluefin killies) aren't quite happy unless there's at least 6 or 8 of them.
The LLO and the 3 Elassoma species are all pretty much live-food only. BBS could be problematic in a large tank with just a few small fish, the BBS may well die before they're found and eaten. What would be the food plan for those?
I love the shufeltii crawdad-lettes. I have 7 or 8 ranging from 1/2" to 1.5" in my 33L "fast-water" darter/minnow tank, and they're just a lot of fun to watch. I suspect there's an underground maze that would put Vietnamese coal miners to shame. (substrate=mixed gravels and sand, mostly with a layer of 1/2" to 3" pebbles on top. I mention this because the shufeltii I've caught have been in rock/riffle environments, although it is also true that's the only place I've looked for them.) My "whoops-now-he's-home-I-see-he's-not-a-madtom-after-all-o-bah" catfish went down a new crawfish hole a couple of nights ago, and five minutes later I saw him swimming at the other end of the tank. I don't know where he exited, but it was not close to the hole he went down. No bad-shufeltii behavior towards the darters that I have seen, and I watch this tank a LOT. (As I type this, in fact.)
HTH - d.d.