Wouldn't it be nice if Windows... would be able to compile its kernel exclusively just for your hardware without having tons of legacy / inappropriate junk spread across your hard drive / memory footprint.
No, that would be pointless. The core of the Windows kernel is already as small as it's going to get and 99% of the hardware support is in the form of drivers which aren't loaded if the hardware doesn't exist anyway. So you might save a little disk space by choosing to not install them, but then it becomes a PITA when you add hardware.
People thought the same thing about the Linux kernel for a while, but the savings just aren't worth it. The "inappropriate junk" spread across the drive is all userland legacy support, you can't remove that if you expect to actually do anything with the system.
Windows is an AMD bulldozer. Good at everything, excels at nothing. Kills your brain too.
3) Wouldn't be nice to have a console-like gaming OS for PC hardware so people could dual-boot or smth. Current Windows D3D technology is a fail. Can't make use of hardware, slow... inefficient.
Maybe, but then how would MS sell consoles? The whole gaming OS thing has been thought of for years, but it's just not worth the inconvenience of having to reboot. The same reason no one likes to dual-boot Linux and Windows either, you just end up using whichever one you're more comfortable with and wasting space on the other.
Bill Gates's invention. The world would have been a better place without him ;-p
As much as I dislike Windows and Bill Gates, he made the PC ubiquitous so he deserves some amount of respect.