scarab SNPC

If anyone can make the scarab from halo 3 a snpc in garrys mod that would be great
heres what it should do:
1)climb over obsticales
2)shoot any npc (combine and rebels alike)
3)destroy it the same way u do in halo 3 by getting on it and destroying the power core in the back
4)custom animations (spider like)
5)shoots a big single laser from the front
6) have a cannon on the back that shoots smaller lasers
7) make it explode when its suppose to die
heres a vid: http://www.youtube.com/watch?v=4ESv_3YMOrQ i hope that vid clears it up a bit
if you could make that for gmod that would be awesome
good luck!