Although all your unit-models are very usefull, they lack in quality of Skins and they don't use TeamColors.
This specific model (dropship)'d be much better if it'd use grey blp texture and TeamColor (can be done with Materials in mdl file); that way it'd change colors.
The next suggestion you can think about in the future, is that flying units could use Global Sequence Translations. For example; this model could be consantly moving up / down a little if the Translation of the specific Bone'd be defined trough Global Sequence. The advantage is that the model won't stop "hovering" during Attack animation!
Alsp think about more realistic emitters during that animation. Also try adding a Tem-Colored-background that'd be seen during Portrait animation...
Those are little detailes, making model useful and more comparable to the Warcraft originals.