Looks have nothing to do with it. People can keep whatever they want no matter what the physical appearance. That's personal opinion.
Fact of the matter is - most, if not all, of the fish in that 35gl tank will outgrow it. Balas reach anywhere from 10-13", the smallest "common plec" will grow to 10" minimum and produce a lot of waste. The silver dollars, Metynnis sp., will grow to about 5 or 6" and are highly active. Not very good choices for a 35gl. If all these fish are to be kept together I'd recommend a 4' 75gls as a minimum. This is without considering the mystery cichlid.