ps. Maybe it's far out in the future, but I'm thinking about ways to get custom made games, graphics, music out there in the 'cloud' so anyone can pull them down and use in their own projects.
I like your idea, keep it simple initially and then build it up. If you aim too high at the start, with respect, you (and anyone else) will fail. I love the expression "bit by bit" which is what you will do here.
As for putting things into the cloud, I've been thinking similarly of late. I have lot of ideas but not enough time/expertise to complete my ideas. My idea is to have a website which allows you to upload your work, whether it be code, graphics or sound/music and you can then share with others. People then come along and select what they need.
My other ideas was to use this for online code generation... I'll explain...
In your code (lets say MADS), you could have a new command which says....
inco myAtariShares /fonts/animals.fnt
inco myAtariShares /graphics/elephant.til
'inco' = include online : So at compilation time, it'll look up a pre-configured link for 'myAtariShares' which might point to www.myAtariShares.com or something like that. It will then download the font and the tile data as it is compiled. It could even keep a local copy in-case that it is removed from the internet.