Bagpipe, yes it would be a Y DNA test. We have several to match with in the Kintyre area as well as on mull. Including a few with credible evidence of relation to chiefs. Yes, you don't know if the male line is unbroken until you test but it's possible. And even if it IS broken, sometimes people find out other things, interesting things, that happened with one of their ancestors. We have many broken lines but everyone is still a MacLean and still part of the project.
Finding out someone is actually a McDonald or Campbell from WAY back is actually fascinating given the knowledge we have of ancient clan history. We can definitely see clustering to find who is originally Irish versus Scottish and see clusters within Ireland and various areas of Scotland. Only the Big Y test is worth taking, the other ones give false matches. I hope you consider testing because we REALLY want MacLeans from Scotland to test so that we can learn more!