While I understand your concern about Brawn/Soak stacking being exploitable; from my experience with the game so far there are plenty of in-rules ways to combat it.
That pin-headed meatwall will die long before they reach broken levels because it does not have the skills to back up the brute strength. As their companions die around them, more and more attacks will be directed at Meatwall the Trando/Droid/whatever and they will die. With all of those points pushed into Brawn, Will is going to be deficient and they will become succeptible to Strain attacks (read Stun Setting).
The management of Strain Threshold can be even sketchier than WT in some cases, since players burn ST by choice. Threat/Despair results causing little bits of Strain damage, Strain depletion for abilities that have a strain payment component, and all of a sudden the players can be stunned with relative ease.
In the case of your Brawny Droid there are societal restrictions in the SWU to take care of it not mention tangible ones. Tanglible fixes being restraining bolts and ion based weapons that are designed to incapacitate droids quickly. Societal fixes being that the galaxy just had to deal with the Separatist Droid armies and there are references in the fiction to the manufacture of battle droids being restricted (possibly abolished) by Imperial edict. IG-88 and 4-LOM being the only 2 combat droids in the Rebellion era that I can recall off the top of my head and I don't think 4-LOM is technically a battle droid, his chasis looks more like a protocol to me anyways. A player droid in EOTE would be pretty much bait for a stealthy jawa with an Ion blaster or restraining bolt/caller.
If the GM cannot cope I think it is a failure of imagination and inattentiveness to the full scope of the rules. I haven't done a comprehnsive read of the beta rules, just the ones available in Beginner box, and it seems like a managable issue. I had a table of players with a cumulative RPG experience of about 60 years who created their own characters using the beta rules and even with a few botched rulings in their favor and I still had to be careful of a total party kill. Shaddai is one of my players and his Trando is formidable but he still got tagged with 2 criticlal wounds by the time they were able to get out of Mos Shutta.
On the other issue brought up in this thread:
In the Beginner box rulebook, Breach is stated as effecting the armor of vehicles and starships. I also take that to mean the 1breach =10 soak negation conversion, that is being bandied about is also in the context of vehicle/starship. Ships/vehicles have deeper pools of threshold than players or npcs so that makes sense. They should clean the wording up so that rules lawyers don't start exploiting crap like that. Pierce works fine to my mind. It will become more relevant as the players progress.