Can't trackers change to using a credit-card-scheme-style "dynamic" tracking ID system (you know, the same way you can tell if a credit card is Visa or MasterCard)? For example, if instead of looking for "gclid", a site looks for "f(query-key) == 39", where "f(query-key) = char1 + char2 + ... + charN % 64". Under this system, each advertising provider simply needs to own a mod number instead of a query-key (Google would look for 39, Microsoft for 23, etc.). You can then have infinitely many tracking keys, that don't even need to be consistent within the same session. At this point, you would probably feel a lot less confident about arbitrarily removing these from the URL, since it becomes increasingly difficult to know for sure that you aren't breaking a legitimate use-case query parameter.