This little thing called a freqking large custom battery to power the display. That's where the SuperDrive space has gone.
Plus as well people want stuff thinner, something has to go...bye bye superdrive.
I admit, I hate paying Apple prices for Ram and HDD/SSD (which is exactly why I'm not paying it on the iMac so I can fit it myself) and have upgraded the Ram in both my MB and MP...
However, I can see these machines lasting a long LONG time...the spec of them is ridiculous. Engadget threw everything at it and said it didn't even show a hint of slowing down.
Quite basically you shouldn't need to upgrade, if I were to order I'd spec 16gb RAM...SSD wise I'm not sure. 256gb is plenty for travelling around with (remember it's a laptop, not a desktop replacement)...anyone who needs more than that is likely to have an external drive knocking around, or has one to backup to anyway.
As far as the battery goes, well I'd just take out the 3 year warranty then towards the end of that have a wing and say it doesn't last for very long, or make up some kind of excuse so they are liable to replace it under warranty and job done