For you hero,
What I was planning on at Siege of Mos Eisley is using the Senior officor leading the Assault; DSS-0956.
About transport, read this:
Instead of depending on machinery that may not function in hostile environments, sandtroopers make use of local creatures for transportation.
You could add a fun aspect, in order to keep the atst running, you need to repair him from time to time:P.
And what I was planning to use also, and you might like too in your map, is this:
A stormtrooper sergeant's pauldron is white while an enlisted stormtrooper's pauldron is all black. Squad leaders, who lead units of seven troopers, wear orange shoulder pauldrons.
(in effect schizo is right

this is just more detailed

)
I have tried this before and has a quite nice effect. You need to hex edit/ignore a lot of strange signs while editing with word pad, the Stormtrooper_pack's for it... well you probably know, nevermind.
Last, in the movie, they seem to use a WIDE variaty of weapons(can be explained in two ways;
-1. More than one dispatchment of Troopers was there.
-2. It looked cool while making the movie)
So why not put in a lot of random looking weapons (watch closely, some weapons look very random and aren't listed on any site.).
Dread