What if you never sent a file again?
Your customer connects to your Stacks once. That's the whole setup.
From that moment, they type a skill name and it runs. Nothing to download. Nothing to install. Nothing to break.
You give them the stack they bought. The starter stack is three skills. The pro stack is eleven. Same connection, different contents, and you decide which is which from a dashboard.
You publish an update at 2am. It's live for everyone before they wake up. No email, no instructions, no version drift.
They upgrade on Tuesday. You add a stack. They refresh, and the new skills are there. You didn't send anything.
They cancel on Friday. You click Revoke. Access is gone the next time they try, and if they come back, one click restores everything.
Skill one is the only hard one. Every skill after that is one click for you, one refresh for them.