this is 150% more cool then I first thought it was.
pros: this models very useful -- it has potential and I like how its a turret boned ''turret'' model. very nifty.
cons: there is no attachment point behind the crossbow on the ground attached to the turret bone meaning we cannot use units (such as mur'locs) as attachment arts to man the turrets from behind, and spin around with the bow because you did not add one, fix that, by adding an attachment point at 0 height behind the crossbow about 100 or so back.
the birth animations kinda lame, look at the Sentry gun for inspiration on a birth animation:
http://www.hiveworkshop.com/forums/models-530/sentrygun-47475/?prev=search=sentrygun&d=list&r=20
this birth animations fast but clean, yet nice. imitate that birth animation if you can, minus the flames.
the death animations also kinda lame, you should emulate this turrets death as well.
the reload half of the animation should not be in stand ready it should be in the other half of attack, the ending half. this is for animation reasons. other wise if somethings attack rate is too high this turret will look glitchy.
I think you should consider using darker textures for the legs of the stand. that or pick better textures that better match the crossbow.
I consider this fairly incomplete but its easily a 6/10 as of now. could be a 9 if you did some more stuff to it.