I totally agree. Like you say I generally hope Maitland does well for Scotland as I was a big fan of him in New Zealand. Same goes with Thomas Waldrom for England. But I think selecting players based of grandparents just devalues international rugby - as its a selection criteria which is arbitrary and constantly abused. Did anyone one of Thomas Waldrom, Sean Maitland, Michael Bent, Isaac Boss or Michael Harris feel evenly remotely English, Scottish, Irish or Australian? None of them lived over there for more than a few years (while they were playing professional rugby) and qualified purely because of grandparents and not on residency basis.
I'd be much happier for these players if I believed they truly felt those countries were their home - and spent more than a year or so before they that became the case. There doesn't seem any point in playing international rugby if unions select foriegners for their international teams.
I don't buy the "well you produce so much talent - so you should share it around". No. That's the easy way out. It's not up to NZ to produce competitive players or coaches for other unions. If they want to leave to play overseas then fine, but don't select them for a national team based off grandparents or even parents. They have to live in the country first. What's even more embarrasing is when these unions try and pretend the players themselves consider themselves from that country because of grandparents. You even had Scott Johnson say that it was actually Maitlands parents who were from Scotland - no sorry Scott, it was his Grandparents, don't talk BS. I'm guessing if Maitland truly felt Scottish he wouldn't have played for NZ Maori first.