I completely disagree that "Pro" implies serviceability. I won't even use the car analogy.
In general, you're thinking "Windows," or what we've been fed to understand as necessary the past 20 years or so with notebooks. Here's how I'd address your points:
1. Bleeding edge resources.
Really by that you mean memory and hard drive; nothing else. And even then, motherboard hardware is limited to some maximum memory and speed standard. I know
you know this, but think about the baby you've thrown in the bathwater. No matter how upgradable a PC notebook is when purchased, it's only a matter of time until a newer, faster,
incompatible speed and/or capacity standard for memory and storage comes to market.
2. Easy serviceability (imagine your hard drive dies in the field somewhere, or your battery can't hold a charge because it's too cold and you can't swap out batteries)
Again, you're only talking about memory, hard drive, and battery; nothing else is serviceable anyway. True, if a Retina SSD crashes, you're up a creek for a while, not like some PC notebooks that have easy swap mechanisms. But I'd say that the ability to swap drives for work (security and/or environment) is probably at least as important as the ability to swap drives due to failure. In that case, an Apple notebook isn't ideal anyway. As far as batteries, goodness - I
wish I had more batteries for my work notebook. Expensive failures over and over. In my Dell notebook.
3. Overall ownership costs going up.
Not sure if this actually helps your argument. I spent way more upgrading my PC over the years than my "unservicable" iMac - yet with the iMac, I never really had the need to. I'm not sure what industry you work in, but it's not far fetched to say that the cost to buy a stick of ram for that notebook the boss approved 2 years ago is much more than if you walked into a store and bought the ram yourself. And again, if you can't upgrade a Mac, isn't that cheaper? Sure Macs cost more up front - but the cost to upgrade over the supposed many years of an "upgradable" notebook's life adds up.
4. Hardware fails, it is inevitable.
Again, if you're talking serviceable components, you're only talking about memory, drives, and batteries. And in all probability, that's in order of failure rate too. This is where the reliability of the notebook and individual components is obviously critical. Purchasing something because it's easier to replace a failed component is smart; purchasing something because it won't fail is smarter. I realize Apple components fail - but I'm much more comfortable with my Mac drives than PC drives - and in practicality, doesn't data redundancy trump that? Whether I can replace a hard drive on the go or not is one thing - having all my data is another - and it has nothing to do with my notebook being serviceable.
5. Losing the option to customize certain components that may suit your needs better.
Again, and again, memory and drives - which Apple
does give the option for customization. If you purchase a maxed-out MBP, you can't do any better than a comparable maxed-out "servicable" notebook anyway.
Every notebook has a maximum capacity for memory and drive space. I think what you a really trying to argue for is not for a serviceable notebook; but a cheaper notebook. Once you max out your serviceable notebook, you're done - no more upgrading or customizing. It's just that with the rMBP, for example, you're given that chance "once," up front (OWC upgrades excluded).
Note that I'm not saying, "you're a raving lunatic and you're so WRONG" - I'm just saying there are nuances that people need to think about. Many notebook owners don't.