I am new to this site, but not new to collecting Legos. But anyway, I am working on a project like this right now.
I already have the sets, parts, minifigs, and instructions in a database. I am working on the front end right now and the queries to do exactly what it is you are looking for.
I am going to release this as an offline app at first to see how well it works with the Legon population. And quite frankly, it's going to be big, like 2 gigs or so, because of the pics, pdfs, etc.
But the app will also allow you to browse all the instructions for all sets, look at their parts lists, stickers sheets, and minifigs included in that set.
You will be also able to browse the parts list, look at the official lego color chart, and browse all the minifigs (because some came as collectibles and are not included in sets)
It's taken me a while to get to this point, so don't expect anything for the next month or so. But I will keep you guys posted.
Zani
