Just wrote an example how the high soak guy can easily be addressed with RAW. Doesn't even require big huge guns, although by my count in docking bay 94 there were 7 troopers, with a LRB and at least one HBR, so it isn't like they don't show up ready to rock in the movies.
But if that very same stormtrooper clique were to then find their attention on another PC (presumably not the worrisome soak-beast), it splatters the poor fool so far into "DEAD", the potential risk of the character sheet spontaneously bursting into flames at the table is real...
So what do you plan on throwing at your players for opponents? I don't think of a squad of stormtroopers and a sergeant as completely off base for potential opponents players in a Star Wars RPG might face. My example was to simply add a glop grenade or two to the sergeant. The stormtroopers could be armed with plain ol blaster rifles like they are.
I'm not certain, but I believe you may be missing part of the point here WRT your solution (which is, quite frankly, a common one) and why it can be problematic.
Yes. You can throw a sick killing squad at the soak-beast to challenge him. But same said killing squad isn't just an inconvenience to the other PCs. It's a death sentence.
Balancing an encounter across the whole group of PCs, when some are soak-beasts and others not, is not as simple as just "throwing scary dice pools of hot blaster fire at them". Because the moment one of the non-invulnerable characters gets caught all up in it, their toast.