Kewl - but...
I would prefer 3d animation with cell-shading. So u can trace it or at least render it as GIF sequences - this way u could make it longer while retain it in 5Mb size. Cell-shading goes along better with flash. Although it lacks the beauty of radiosity, but i think what ppl is looking for in flash movie is the way the camera can rotate and do the perspective view which is very darn difficult task in Flash - and 3d animation with cell-shading can ease this. It also relive u of doing somuch texture details and save u render time.
For ur animation- I'd say the tank lacks the ttx detail , also the Hydralisk. The way the hydralisk move doesnt look good. U should make the tail wiggle while it move and do the constain to the surface so the body doesnt intersect the ground. Anyway, this scene rockz. :)