I guess if you get in touch with the people from IMSLP.org, then the work to get data added to your or their database will benefit from joined forces. To fill gaps, the users themselves are often pretty good volunteers to fill in missing data. Many will do it just to say Thank You for being offered such platform, from which they themselves benefit a lot. You administrators would mostly do the quality assurance.
But, the informatics aspect is what currently seems to urgently need enhancement in all this kind of projects/platforms: if all the data would be stored in a relational database, then to the users could be provided some (for instance SQL based) frontend for searching it.
Each user would design the output themself. Some will query the database in order to receive as an output a list of composers organized along a timeline, or time span, era, alphabet, amount of compositions, amount of videos, genre, mood, free availability of sheet, difficulty, whatever, or any combination out of this like age of the composer when having composed X percent of his works, easy level pieces according to which´s source grading (US american, Canadian, British, ... music school society, or which´s book author opinion, ...) in the key d-minor.
You could prepare common queries as available default questions, but could additionally allow the users to formulate their query themselves. I think, this is what is really missing at the moment. If it is a relational database, then it will be easy to anytime add attributes to the pieces (videos, mp3s, midis, sheets, editors, number of bars, whatever, user comments, pianist who are practicing/playing it), and all this would rightaway be searchable as soon as attributes become filled with data.
Give to the interests the proper platform, fill in some basic set of starting data and first functions, and then the project will be a winner (see Youtube and Facebook for instance). Their informatics is based on a pretty simple set of attributes, which the users happily fill with data.
And with the IMSLP their would be a huge set of starting data already be available...let´s find somebody who is able to program an enhanced platform which allows to add data and to query for data!
learning Piano on my Roland HP-505
before playing Drums in adults bluesband on handpicked set; before crashing E-Guitar in kids garage band; raised on home entertainment Organ and Keyboard models Eminent Solina P240, Farfisa Maharani 259R, Technics KN800, and on Mouth Organ, Recorder and Accordion