Arrow keys are almost the same to WASD, they work very well.
An easy upgrade would be only if Asus will use an 680M in a future G75 release. I think not.
670M already exists, so that would be easier, but only if you find a real cheap one. And remember that Asus seems to be using different MXM standard, so not every card will work.
About upgrades. I also have a Clevo. Let's consider you will not upgrade every year. After a few years the entire laptop will worth very little and the tech will be a thing of the past. I've seen this with Clevo. With the money for a new CPU-GPU-HDD-RAM I could get a much better laptop with warranty and not an old patched machine. You really don't win that much with upgrades if money are the issue.
And this entry 3610QM is just amazing. 25" to encode an entire album in FLAC. That is insane. 20' to encode a DVD so I can take it with me and during this time I can play games with best settings.
ASUS is better, yes, upgradeable video card - no. 😞 Can't you get the 670M in the BestBuy G75? That is the best card that ASUS supports, because the 680M uses so much more power. Try it in BestBuy, see if your mnatural position is comfortable. Everyone games differently, so other's advice is only so good.