Internal users can only access what their role allows, so you could just remove all roles from the seasonal workers User, which would effectively disable the accounts. 

What version of ScreenConnect are you running? The Session folder was deprecated years ago, so you are safe to move those to an archive or delete them.
Session.db at 2GB should not be an issue, but i would make sure that you have maintenance plans enabled to keep it trimmed down:
Database page - ConnectWise

This is easily accomplished using the following Session Filter:
UnacknowledgedEventCount > 0

Session groups filter reference - ConnectWise

Hi everyone,

Our architecture team has some ideas on how this could be implemented in the product, but we'll need to do some additional discovery to determine scope and risk. If we determine it is something we can accomplish, we'll schedule it for development, but as of now no timeframe for that.

Hi Everyone,

I am waiting for feedback from my architecture team, as you can imagine they have had a busy couple of weeks, so their responses have been delayed. As soon as I have more information, I'll post it here.