My iMac has multiple cores, and I think all Macs do. Does the KM Engine have any coding that takes advantage of this? For example there are some actions that are CPU-intensive. I have no experience with multi-core programming so I don't even know if this is possible. But it seems to me that some actions could benefit from this idea, perhaps the OCR, Find Image and Execute Macro (asynchronously)" actions. I infer from some of the threads I've seen that the Engine does not spawn off any tasks, and I'm not sure why it couldn't.
I think the simplest way to make this feature available to users would be to introduce a new action that looks exactly like "Execute Macro" but instead says "Spawn Macro" and rather than run in the KM Engine is run as an external task. I can already see some complexities in handling this, but it should be a valid idea for discussion.