If it's “among friends”, isn't "change the script" out of scope?
You either trust the client to do the requested work, or you don't. If you can't trust the client to use the appropriate CI script version, then you can't trust anything the client responds with.
An example of this is how hacked DVD/BluRay drives work, where they fib to the driver about what byte is in which memory address.
You can issue the work to multiple clients, and treat it like a node failure. If you have a quorum of executions then you can trust that result. However, that's similar to the disallowed proof-of-work requirement.
No matter what, the client has to trust that the server isn't out to get them.
You either trust the client to do the requested work, or you don't. If you can't trust the client to use the appropriate CI script version, then you can't trust anything the client responds with.
An example of this is how hacked DVD/BluRay drives work, where they fib to the driver about what byte is in which memory address.
You can issue the work to multiple clients, and treat it like a node failure. If you have a quorum of executions then you can trust that result. However, that's similar to the disallowed proof-of-work requirement.
No matter what, the client has to trust that the server isn't out to get them.