ding ding ding ding ding we have a winner!!
First of all, no, its not designed for you. Apple took a machine that was awful at being a jack of all trades and specialized it. Now its a screaming compute machine that is 1/8 the size of its contemporaries.
Not only that, but based on what you described as your professional work flow you don't even NEED the power this thing has, an iMac has plenty of horsepower for what you need. Apple doesn't give a **** that the machine doesn't satisfy the requirements of the hobbyists that bought them and didn't even utilize half of their power and only bought it because it was the only tower Mac in the lineup. A lot of tasks that used to require a beefy computer can now be served by a iMac or Macbook Pro, that is how much technology has progressed, everything is becoming more and more integrated, and what used to require a beefy computer can now be done on a run of the mill desktop.
So keep on crying for upgradeability because its falling on deaf ears not just with Apple, but all the other OEMs who are feeling the pinch and have to save money somewhere. Making a system upgradeable adds cost to the system, it also means more points of failure, contacts could be damaged during the upgrade, a user could put an incorrect part and cause the thing to short. Not only that, but the number of people that even upgrade is tiny. Its just cheaper to integrate everything, and saves them a lot of headache. The flip side is that if something breaks, you are at the mercy of their customer support, which is something all the PC OEMs are gonna have to step up on if they continue down the path of integration. Hobbyists are a minority,
you no longer dictate how computing works like you used to back in the day. The masses want a box that just ****ing works, the pros want a ****ing box that lets them do their job and not worry about the internals. That's not making them money.
Second (and this is more for the idiotic posts i've been reading all over the thread and not you), its a ****ing workstation, this is NOT some really fast PC that you could build yourself for cheaper with parts from Newegg! That means that first and foremost it has to be reliable and last for years upon years. The thing has ECC RAM just for that reason, and those FirePros?
They also have ECC memory, they may share the same architecture of the gaming GPUs, but the similarities end there. You pay thousands of dollars for these things because they have been validated and are designed to be as rock solid stable as possible. If you're a business whose lifeline depends on workstations like the Mac Pro, having a stupid fast product that works all the time without downtime trumps upgradeability six ways through Sunday.
Yeah, that sucks for the computer hobbyists, who wanted an xMac for years, well this isn't an xMac, deal with it. Unless your work involves compute intensive tasks like protein modeling, or compiling a massive program, this isn't for you (I hope Xcode will eventually utilize the GPU for compiling, ah but a pipe dream). Its time to consider new options, because whether you like it or not, integration will continue, and as we should all well know, Apple isn't shy about moving towards future before everyone else and leaving the old stuff behind.