Point Cloud Processing - Accurate decimating

Hello everyone!

I'm currently working on a point cloud based project, where the goal is, to compute a interactive model of a small town, freely available over the internet. 
The problems I'm struggling with, are the data capacity of the online application.

There are many tools to mesh point clouds, and also to decimate them, but if you have to decimate to 5% or so, it usually gets really messed up and no longer recognizable.

The end model can really be abstract, but the shape defining edges, like house corners, should remain as accurate as possible.

Maybe someone has an idea how to process this with the help of Rhino and Grasshopper? Would be great.

Thanks a lot,

Mat