To that end, I ran a simulation of the Battle of Hoth today (well, the first three rounds of it... it's a big battle), and made a few discoveries:
The vehicle rules I have going so far are SPOT ON. The AT-ATs felt and behaved like AT-ATs in combat, the snow speeders felt and behaved like snow speeders. An AT-AT was able to one-shot a snow speeder, and the speeders had great difficulty penetrating the armor and shielding of the AT-ATs, but the numbers were all manageable and generally small.
I had to find a mechanical solution to "Luke gets an idea to trip the AT-ATs", and the solution solves many problems at once. Tinkering (the gnome ability... or whatever I end up calling Gnomes... right now I'm leaning towards the Gno because they 'know' stuff... get it?) will allow you to make a supernatural Feat (target 30) to discern a weakness in enemy mechanical instruments, or a mechanical solution to the problem.
I know that Luke isn't a gnome tinker (or maybe he IS... that's the big reveal of Episode 8, or so I've heard), but his use of mysticism allows him to spend a point to make a CHA check instead of an INT check to mimic a Tinker check by using 1 of his 2 stunts this turn. In this case, he has CHA 14 (he's just an apprentice still, probably level 3, giving a +2 shift to his starting CHA of 12 at character creation). He needs to roll a 16 on the die to make the check (not likely, but possible) and does. He intuits that the walkers are weak on the top, and they could be tripped with tow cables. The GM resolves it this way:
The GM reveals that a successful attack with tow cables (requiring an attack roll at -2) will allow the speeder to spend the next round winding cables around the legs. On a successful Control roll, the pilot will trip the walker, which will disable it, and give +4 to attack rolls against it, in a location that has no shielding, and where the hull is only 2 points (instead of the 10 points of the rest of the walker). Any successful hit against that spot automatically scores critical damage.
Basically, this allows only tinkers or templars to have a chance to do something like this (and Tinkers more often and with more success, because of their nature). Others (like Solo or Chewbacca) probably have picked up tinkering as a talent, and could also try this.
Even better, it gives the GM a lot of flexibility to decide things on the fly that will alter the outcome of a battle or change the dynamics in play dramatically. However, it requires a successful check by someone with exceptional training or ability to set the wheels in motion, and it can't be done all the time - there's some resource requirement to get the idea. In this case, Luke didn't just 'think of the idea', it was inspired by the living force.
The other takeaway (for the GM section) is that not all battles are about 'winning'. In this case, the goal is to hold off the walkers from getting to and destroying the shield generator that prevents bombing and dropships from entering from above. Your goal isn't to win... it's to keep the enemy from getting to a specific point for as long as you can, or holding them at bay for a certain amount of time until the rest of your group can escape.