Module::Pluggable is core, so the only burden would be (again) upon the plugin author. Personally, I wouldn't check whether a class/package uses Moose but rather just do

my $metaclass = eval { $class->meta };
if ($metaclass) {
};
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that way non-Moose things have an option to work as plugins as well, as long as they have:

sub meta {
...
}
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which returns something "good enough". For example the following should work for your use case as a minimal class:

package My::Plugin;
sub meta { __PACKAGE };
sub does_role {
    my ($class,$role) = @_;
    $role eq 'chatbot'
};
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