I think a generalized bonsai care sheet in the beginning with specific species care after is a great idea. The only thing I would do is add more trees to the species guide. Members of this forum could fill it with their trees, using their care instructions for that specific tree.
One problem I have with some bonsai sites is that they only list the most popular trees, therefor giving beginners the impression that those are the only suitable trees for bonsai. I along with other members here have some very odd trees that aren't listed on any site.
We could fill the species guide very easily.
That's my 2 cents worth