David,
It will take some experimentation on your end to see what is possible, and what will work best.
Noting primarily, that Land F/X will always keep all plants at 0 elevation. So the workflow will include a final process, which could be very similar to our Shadows or Plant Outlines, that will place all plants at elevation, with COGO points.
But in determining that ideal process, the above links should help. I think it would save a step to just use multi-view blocks while designing, to have that step taken care of. You should have little to no issues using multi-view blocks with Land F/X.
Then dropping the trees to the surface, also seems easily handled by the second link.
So the only process that is a head-scratcher, is the COGO points. The third link has a slightly roundabout process to accomplish it. There may be a better process, and it may well even be as simple as defining the multi-view blocks as COGO points in the first place.
Let me know what you find out, and we should easily be able to integrate some additional functionality into either the 3D Connection, or an entirely new command.
--J