I'm sure there is a variety of reasons why the nMP is a difficult choice for many, but this is certainly one of them. And it would be something that could easily be fixed. If Apple offered a build option where the GPGPU, that many do not need, is replaced with a drive bay capable of housing 3 M.2 sticks, that could fix this issue. And it can't be that hard, OWC built one. And clearly if people are getting by with the iMac's single mobile GPU, then one slightly hobbled desktop GPU should suit those people as well. And do so without forcing them to sit in front of beam splitting mirror display.
But it will never happen. Everyone in this thread needs to realize that Apple is just not a computer company anymore. They are phone company first, a tablet company second, a services company third, and for the time being a computer company fourth. With gadgets and gizmos gaining ground.
Further if you break down the computer segment, they make laptops first, iMacs second, Mac mini's third, and way down at the bottom Mac Pros. At this point the MP market is an after thought of an after thought. The nMP was a sacrifice thrown to the hardware engineering team to give them a challenge, and an opportunity for Apple to wave their think different design flag in everyone's face, thereby showing everyone they still have the chops they had when SJ was less dead.
And there is the mental vise that Apple has itself in these days. They can't make anything simple and practical no matter how well designed it may be, for fear that pundits will harp that Apple doesn't have it anymore, or they have lost their "mojo", we new it was just a matter of time before Apple became ordinary. How much ado do you think there would be in these threads if Apple still sold the cMP and the nMP? Not a lot i expect, both camps would simply choose what suited their needs. But Apple couldn't do that, because it would definitely be the Mac Cube all over again. So Apple eliminated that possibility, leaving the nMP as the only option for a Mac with a high-end, OK medium end, GPU.
So here we are. Will something the size of the nMP eventually provide all the CPU, GPU, storage, and flexibility for just about every power hungry user out there. I'm sure someday yes. However that day still seems years away.