I am reconsidering how the RP starts. Instead of there only being people from one group of friends, I'm thinking maybe the scientist has been kidnapping teenagers from all over Los Angeles, and there might even be other groups of shrunken people at different locations. As for the group that the RP will focus on, instead of it being just a few friends at a Starbucks, it could be dozens of people who were at a secret graduation after-party that was held in a large abandoned industrial plaza. The scientist owns the property, but presents himself as merely Mr. Dude. He lures the crowd into what he claims is a prototype holodeck like in Star Trek that he's been working on, but it's actually his Morph Chamber. The crowd is shrunk down and they lose consciousness almost immediately.
When they awaken, they are in the backyard at his house, the entire crowd trapped in a plastic bug container, and have been changed into outfits similar to Squid Game. After his video chat speech that was previously discussed, one side of the container drops down to form a ramp out into the yard. When some of the people are hesitant to leave the safety of the container, the scientist laughs and is like, "I thought you might be reluctant to venture out into the dangers of the yard, so you need a little more... incentive. Say hello to my little friends!" He flips a switch, and another wall within the container opens, revealing a second chamber holding several aggressive mutated Mantises. This causes everyone to scream and flee the container, but a bunch of people are either ripped to shreds by the creatures or scatter into the yard and get killed by other things.
My idea for changing it to this is twofold: One, so that we have some "expendable" characters for the sake of the story; and two, so there is a backdoor into the RP if other people show interest after we've started. For instance, let's say after a bunch of people are killed or scattered, our main characters form a solid group of ten people. Let's say we're already many posts into the RP and someone else wants to join. Well, that new character can be someone who fled into the yard at the beginning and got lost and is just now finding our group again. There could be several other characters scattered about who can join up with our group later on. I think this is a wise idea as it leaves the option open for new co-writers throughout the entire first arc, but what does everyone else think?
Also, if you're curious for size comparison, here is a video from on of my favorite YouTubers preparing for a fight against the Mantis in Grounded: