If detection is an issue, how about letting user manually place the mark so that Nitrogen would know where to put the bridge? Would that make it easier to start?
Also, I mentioned that thread because the bridge the OP showed in the screenshots looked like they could be repeated to make the actual bridge longer if needed and they do seem to have pillars for better stability, so making them longer shouldn't be an issue.
Lets see, I will add some logic eventually.
Currently, you could add the bridge POIs manually by editing the prefabs.xml
something like
<decoration type="model" name="bridge_asphalt1" position="654,41,-247" rotation="1" />
where the second parameter in position is the hight (wich you probably need to run some tests to find the correct one)
those are the bridge POIs currently in vanilla:
//bridge_10x10_end_01,BRIDGE,2,-1,10,18,10,
//bridge_10x10_tile_01,BRIDGE,2,-1,10,18,10,
//bridge_asphalt1,BRIDGE,2,0,39,11,11,
//bridge_asphalt_broken,BRIDGE,2,0,39,16,11,
//bridge_concrete1,BRIDGE,2,0,39,11,11,
//bridge_wood1,BRIDGE,2,0,39,11,9,
//bridge_wood2,BRIDGE,2,0,32,10,7,