Just want to make a quick update on this, because I feel this is extremely important for osu! I decided to just start working on it myself.
I'm not a veteran mapper by any means but I've been messing around with it over the past year and think I've got most of the concepts down at the most basic level at least. By no means will my work be a finished product but by laying the groundwork and establishing an outline for the progression of a career I'm hoping it'll push more experienced mappers to contribute to my work in whatever way they feel like. Expecting someone else to take up the whole project from the get-go was unrealistic since there's so much more than just mapping songs involved, but having a draft in place where mappers can submit their own replacement maps or just suggest changes will probably spark more enthusiasm in the project.
Since it's intended for this to be bundled with the game in the future, all maps are of songs in the featured artist section for legal reasons, and all artwork for backgrounds/storyboards will have to be either original or official artwork from the artist of the song. This project is something everyone can contribute to. It won't just needs maps, it'll need original artwork and storyboards, full original skins (since customization is a big part of osu I plan for the first iteration to award skins at various stages along the career as both a reward and incentive, as well as an introduction to customization - I don't know if this is something that could/would be implemented if this ever got integrated into the client, that's going to have to be discussed) and A LOT of play testing from players of all skill levels.
With that in mind, once the project is a little further along I'll post it in the beatmap projects section and invite everyone to contribute, so keep an eye out for that.