The first problem with this is that when you start to break down a certain forum into too many sub forums it makes for a really messy board. I've seen other forums set up like that, it must be totally disorienting for a beginner if it confuses me. You could have a separate section for discus, as well as angels, which require some specialized care, apistos come to mind, and oscars would be a big one without a doubt.
The second problem is that the care needed for some species overlaps with others, and by learning about those other species it broadens the aquarist's knowledge base, making the care of their particular species easier. I've studied up on discus over the years, and apply much of that knowledge to angels. The knowledge I have of angels I've applied to apistos, and I'm sure apisto knowledge & ram knowledge have much in common. Caring for oscars is going to be very much the same as for any of the other largish New World Cichlids.
I've also found, and this applies to more than aquatics, that if you focus too narrowly on something you risk missing something totally obvious, and this something could be detrimental to your situation.