How about the type of modularity more than one user has asked for, the ability to switch off PCI-e GPUs not in use on a desktop system?
Sometimes I need to max out the number of GPUs for Octane rendering, at other times I may want to run multiple cards in SLI/Crossfire for gaming, and at other times I may only need one GPU for MadVR, or even only integrated as I'm just browsing the web. In addition to raising running cost having many GPU running in idle is total waste, non environmentally friendly. With four 980ti's it's 280 watts just sitting idle, each additional card adding 70 watts. Sure the next generation GPUs are going to be more energy efficient, but it's still a waste. I've seen arguments that it can't be done on the PCI-e standard. Well, change and evolve the standard then.