Agreed. It could well be that an unstructured tag system of entering metadata is the better way to go, at least for some of the more esoteric information, rather than a strict hierarchical classification system with enforced data entry rules. There are distinct advantages and disadvantages to each. We probably don't need to decide that yet. We should probably just begin by organizing the wish-list, and then figure out what is doable from there.That'll probably be better as a tag than a general category. So, for example, you have a string lib that falls under Strings / Sections and it has tags like "bartok", "pizz", "chamber", "medieval" etc. Then maybe you can have a tag cloud or a search just for tags. Then you can add what you think is important at your leisure without filling too many fields when submitting. Articulation lists can also be pasted in a text description field. So, you have both tags + text to search without having to list every single articulation from the get go.
Unless someone has already started on this or really wants to do it, I volunteer to try to assemble the points expressed so far into a sharable on-line document.