I think there is room for such a project to co-exist with wikipedia, but I think you're vastly underestimating the human obstacles to creating something that is not just a weak half-clone of WP content.
The chief problem I see is to get some sort of cross-discipline cooperation. For instance, FishBase has made a good start with fish, but the database entries for beetles or plants will be mostly different; sure, there is some sharing, but the coleopterists' approach to taxonomy is (seemingly :-) ) rather more chaotic, and, well, the botanists have seven different ways just to define the concept of "species", not least because plants easily do the equivalent of crossing humans with tamarins and getting fertile offspring, and molecular info doesn't necessarily demystify either. So you're talking about pushing all of these specialists into a single framework, and if they don't fit well, they're not going to participate.
So before talking to developers about software, you need to talk with people in different areas and get an agreement in principle. Could the FishBase guys sign on to import their data into a cross-phylum project? Are there coleopterists able and willing to mechanize the immense number of characters that differentiate their subjects? Will specialist experts even want to participate in a wiki that anybody can edit, or will they only want a more controlled environment?
And finally, what content would this have that is not just as appropriate for WP, and do the WPers agree with setting that boundary? For instance, the full list of papers reporting every sighting of a species of plant seems too detailed for WP, but I could imagine a parallel set of "dig deeper" articles that go all out on that sort of thing.
Stan