I can think of no faster way to turn Commonwealth realms into republics than for Charles to ascend to the throne.For those who want to see an end to the monarchy, Charles will be a godsend. As you say, he is likely to meddle and cause a constitutional crisis before long. The one thing that worries me is that a change to a republican system would come all too quickly, rather than taking a sufficiently long time for the options and pitfalls to be thought through.