Have fun painting up 900 Termigaunts! This list would make a TON of them.
I looked at a list similar to this - two troop Tervigons and three Trygons - and I just couldn't make it work. I kept running out of points for all the stuff I wanted to add.
A strong Tyranid list right now NEEDS Doom in a pod, Swarmlord/Hive Tyrant, and at leat one unit of Hive Guard. After that you have quite a bit of room to add other stuff.