Trump: "Seattle would be so easy to solve."
Once time has run out for Governor Inslee to act, I would probably do what you suggest, as well as jam their phones. Not sure if they would let residents leave or not.
They have had 'medical volunteers' during their protests, I guess who patch up minor injuries, but probably don't have a lot of supplies available aside from maybe raiding a Rite-Aid.. Once becoming desperate, it is certainly possible they could resort to holding people hostage. Raz Simone seems capable of turning against those who are there that support what is going on, especially if he sees it as a way out.