[spopejoy]

> I also need to accept transactions signed by at least one of two keys.

Keysets are designed for precisely this; what's more this rule can now be persisted.

> anything more complicated would go outside of the system you have designed.

Always a possibility of any PL, especially running in a blockchain. Pact makes less assumptions about use cases than most however. It's imperative, allows functions and modules, and offers a database metaphor. That handles a fair number of things.