If you view cricket purely as a profession then that's absolutely 100% right - and I myself took this view completely until pretty recently.
The issue is whether sport is different to other professions. In some ways it unquestionably is - cricket does not exist primarily for its proprietors to make money, it exists because it's something people love watching and being involved with. It's a question of how far do you take these differences. Ethnicity and birthplace are indeed totally irrelevant for my money. But some form of long-term residence, as I say, is an idea I'm increasingly becoming in favour of.
None of that makes cricket in any way different from other professions. Pilots, for example, earn a lot of money but I think you'll find there aren't many pilots who don't love what they do yet fly in many countries. Of course, we're talking private industry here and they don't represent a country per se (some airlines do, less than there used to be though) but I think that's not really that important a distinction.
The only way in which sport differs from other professions is surely that of the fans/pundits/spectators. And, if I was a player, I'd obviously take the views of those people into consideration but the ultimate decision for how my career goes would be up to me. Let any country impose any qualification rules they want, sure, but if any player was prepared to throw their hats in another country's ring, there should be no restriction on them from doing so as there isn't with most other professions. Certainly, no player should be subject to some arbitrary rule(s) imposed by misty-eyed nostalgiacs just because it isn't confluent with their cricketing worldview.
The whole 'it devalues the meaning of international cricket if players can country-hop' reminds me of the argument used against gay marriage, that allowing gay people to be married devalues the sanctity of the marriage institution. In the same way that there are plenty of heterosexual couplings which do that (Brittney's right to 24-hour-long marriage to that guy in Vegas must be sanctified, after all), there are plenty of examples of guys playing for their country of birth who do their level best to devalue the 'institution' of international cricket.
When it comes to corrupt or unethical behaviour, whether you're playing for your country of birth has no bearing and forcing people to pick a side and stick to it, conversely, does nothing to guarantee the protection of the institution, only instilling a false sense of security if anything. Hansie Cronje would be the archetypical example of what I'm talking about, really; well-liked, professional, talented, corrupt beyond belief. Not that I'm a fan of the institutionalism or nationalism associated with international cricket but I just find such an argument to be specious.