This is not a new kernel, and there is absolutely no way in which moving to a BSD kernel would solve anything at all.
The NT kernel in and of itself is very small, simple, and remarkably well designed. The Win32 subsystem is what is horrid, and that's 99.9% in userspace. There's no reason that they can't create a whole new subsystem along side Win32 where they improve everything, but I don't see that happening.
As said in a sibling comment, Windows Internals is a must-read. However, you are correct -- NT4, 2000, and XP saw the addition of lots of stuff inside of ring0. However, most of that was independent of the actual NT kernel, and since Vista the trend has been reversing in a huge way. There's more in ring0 than there was back in the day, but a lot of stuff has been moved out, e.g. many drivers, even video drivers. The new (relatively speaking) usermode driver framework makes it trivial to write drivers that don't run in ring0, and the kernel now has fewer dependencies than ever.
NT has had some growing pains architecturally speaking, but it's been handled remarkably well. Probably the best thing to ever come out of MS, especially when you contrast it to the mess that is the Win32 subsystem.
Totally, totally agreed. I wish the patent situation weren't such that an interested party (e.g. me!) can't go and implement this. ZFS and DTrace (the ultimate reverse-engineering tool) on Windows would make me the happiest man on earth.
MinWin is NOT a new kernel. It is a subset of NT. Drop the binaries into IDA and look at it yourself, or dig around for Russinovich's talk on the subject of how they disconnected all the dependencies to build MinWin. Even Wikipedia disagrees with you: "MinWin is not, in and of itself a kernel, but rather a set of components that includes both the Windows NT Executive and several other components that Russinovich has described as "Cutler's NT"."
As for virtualization support, you're wrong on two counts: 1) with the creation of Hyper-V, a number of facilities were added to NT to support something akin to paravirtualization, and 2) MinWin has absolutely nothing here that NT doesn't have, being a subset.