"a viewer-based function that allows you to make meshes just like you can make prims"
I remember an inworld presentation of some ingenious big company people who tried to visualize 3D geometry by meshing up triangles made from box prims. So pityfull! Imagine what could have been reached during last four years since 2006 when many companies tried in vain something usefull to do with VR environments like SL. Imagine some group collaboration enabled mesh generation, the possibility.
Or, think easier ... a similar functionality to Paint.exe
Doodling on prim surfaces, painting right into textures. Don't focus on "artistic quality" it would surely turn out like painting with fingers ... or Jackson Pollock style ... but how about the shared experience? Information distribution. Even by placing some letters into a texture using crude texture painting tools inside SL we would have gotten rid of that awwwwsome hoovertexting (which looks odd).
Media on prim didn't changed SL much besides, my recognition, media streaming from youtube vanished shortly afterwards. Placing a webpage onto a prim so far did nothing. Or nobody uses. It just doesn't feel like "inside SL" if it isn't. It is not. The data remains somewhere else.
Doh! typed that twice! My first one has been more written by heart, this one by hate. SL just ate comment editing ... by jumping through some silly opensomewhat login process, and failing with an error message heroically. I really despise how stuff turned to failure everywhere. Posting events currently causes similar struggles ... censoring of Event descriptions running havok. support http://jira.secondlife.com/browse/WEB-3049