This is going to be a great-looking tank. I love that wood, and although I think the stones need to be rearranged a bit for a more natural look they will be perfect. Generally speaking, stones need to be lying down on their largest surface to look "right" to me; only rarely do you see a stone in nature balanced on end.
Softened a bit with plants...maybe some Java Moss for the wood...this will be nice!
The filter is what it is; maybe best to conceal with plants? Hiding a filter with rocks/wood usually ends up drawing even more attention to it: "What's behind that weird-looking pile of rocks in the corner?"
I know you are more or less discounting them, but I am voting for Firemouths; I love those fish. In large community tanks I have owned in the past, I had breeding pairs of Rainbows, Firemouths and Convicts all industriously "being fruitful and multiplying" and IMHO the Rainbows are so docile and non-aggressive that they are almost un-cichlid-like. The Convicts are the exact opposite, a bit too pushy especially in a small tank. Firemouths are the most colourful and display just the perfect mix of gentleness and aggression to make them interesting. Get 5 or 6 young'uns, pare them down to a single pair as they grow, keep them with a small group of Swordtails or other livebearer (I'm a Goodeid fan myself), and you will have a lovely display that should satisfy all 3 people involved.
Having said all that, I have never even seen Nanoluteus or Myrnae and if I found some in a shop might be hard-pressed to pass them up...instead of, not in addition to, the Firemouths. Whatever you choose, stick with only one species of cichlid for this tank.
Tough luck about the Blackbeard Algae; disgusting stuff. I know some folks seem to like it if it's kept under control, but I can't stand it personally. But, of course, I actually kind of like Hair Algae, so...different strokes, etc. Good luck with the tank, I hope you keep this thread updated.