DS2:Alien vegetation

I am putting together some bases of alien vegetation using large tree seeds
that I have found in my local park.  They resemble giant pods at 1/300
scale and should look suitably alien as well provide cover for troops. Has
anyone put together some house rules for alien plants. Am thinking on lines of
these being exotic ancient pods that take hundreds of years to grow (hence the
massive size). They also on occasion emit noxious gases that while not
deadly to PA or vehicles, could be fatal to un-armoured troops.  Maybe
if any infantty base comes to within an inch of the pods, you have to throw to
see if they are emitting such toxins (on D6 if you throw a 1, then you have
been unlucky enough to enter a cloud of the stuff). Then you draw one or two
chits. Troops would probably have some kind of gas mask equipment so you would
have to be unlucky to throw a 1. While the remote risk remains, the pods will
provide excellent cover and cover LOS. Blasting them with a heavy weapon would
not help release the gas as it comes from deep below in the root system. Just
an idea.

dave t