Comment from Sanderd17 on 2 February 2015 at 22:26
Sorry for speaking English, my German isn’t good enough.
Do you know about existing in-browser rendering projects? There’s KothicJS, and Mapbox is also developing some js libraries. These work with quite good data formats (a lot faster than plain osm xml), and also pre-filtered data, but it’s still slow for certain hardware and browsers.
Or just try overpass turbo with some big resultsets. It makes panning and zooming a pain when you want to display a few 100 points.
So those things are tried, and need some time to develop.
Next to the slow browser rendering, you still need a server that filters the data (when you zoom out to see the world, you can’t download and view the entire database). That filtering needs to happen based on a stylesheet (on what level do you want to see which roads?), and the filtering will also be slow (imagine filtering the entire world just to extract to motorways). So the filtered data needs to be cashed.
So in the end, you still need a server that processes all incoming data, and that has to redo the work when rendering rules change. Exactly like a rendering server.
I’m not saying that the things you mention are impossible, I’m just saying that they have been tried, and either are found too difficult or too slow for now.
Comment from Rondom on 3 February 2015 at 17:28
You might also do something like this using Osmarender. Relying on XSLT you can render any OSM-XML given that the XML references the Osmarender-XSLT-Stylesheet.
Still, have a look at Kothic for a more current, less historic approach ;-)