Despite the possibility of setting a base URL for each domain, it may be interesting to allow developers to create complex domain access rules. The behavior should be kept the same as we have today: if the user is accessing a disallowed URL he/she will be redirected to an allowed URL.

A filter is probably the best solution do achieve this:

add_filter('multiple_domain_redirect', function ($url, $domain) {

    // URL verification logic.

    return $url;
}, 10, 2);