Johann,
I have some rough code that needs a little more work and then it can be tested - should be available in the next day or so.
I've no ready solution, but I've looked into the code. My solution would be really simple:
In LineSplitter.clip() simply dont create a Coord but a CoordNode(x,y,n,true) for the newly calculated border node if the line is a road type. With this change you will get a border node at each clipped road, without any additional tags in the osm file.
I don't think that will work - I think you have to clip the way before you generate the nodes otherwise the road will have the wrong number of nodes. I was hoping to put some more time into this before posting a patch but I'll post it anyway. Remember, you will need a bounds element in the OSM file to get a bounding box to clip to. Cheers, Mark