Thinking about alternative stats, I think that there are many approaches that would work fairly well for ICRPG.
One would be to adopt the four attributes from Shadow of the Demon Lord that has already been mentioned: Might, Agility (or Finesse), Intellect (Wits), and Willpower (or Spirit, Resolve). Rename as needed. If you believe that “wisdom” things like sensory perception is distinct from Intellect, consider adding Perception as its own attribute.
My mind also keeps going back to something that Hank mentions quite often when he talks about his core principles of ICRPG: natural language. Natural language lies behind a lot of the terminology that Hank utilizes for ICRPG: easy and hard rolls, effort, near/close/far distances, etc. So I have wondered what more natural language would potentially look like for the ICRPG stats. I do believe that other systems come close. For example, Savage Worlds uses the stat called “Smarts.” This seems like it fits the criteria for natural language, where we may say that a person is using their ‘smarts.’ But we may likewise say that a person is using their “Brains,” which is another term we could use for the same general area as “Smarts.” Either Brains or Smarts seem like terms that a new player could EASILY pick up and understand.
From there, I am less sure as that obviously depends on how many stats you want. I would favor 4-5 stats since that minimizes redundancy and speeds things up. But an approach that adopted more natural language for the stats seems like a good fit for ICRPG.