a auto scene fill add-on; something like ANT landscape addon on but with the stuff that goes with it, there are alot of open source softwares that makes trees, grass, mountain for you, so all you need to do if you have that addon, is to choose the type of land (ie. montain range; low land; marshes etc. and then change the height of certain points, then the addon would use some real life data and place trees in places that trees would grow on, there are also alot of formulas regarding to population dispersion;
this would greatly improve blender’s goal orientation because for now, most of the people still need to make the whole scene up even though they have finished what was intended
if that’s too much, maybe just something like, from a plane, the user shows where is ground level, where are there levels of water, and make 2 points, where is the ground level, and another height in meters, then the addon would place the likely plants into the scene