If your goal is whole-system reliability, there's way more low-hanging fruit than the kernel. In the last five years I've had two kernel panics. It's so rare that I remember both times it's happened. But hardware failures (at least one hardware failure of some kind a year) and application crashes (once a week or more) happen all of the time. Hardware is a complex beast but many application crashes are significantly improvable by some other low-hanging fruit (say, better crash reporting for developers)
But if your goal is absolute, near-100% reliability, you will eventually have to do something about the kernel.
Also, if you look at the design of Minix 3, they do address many of the concerns you mention. There's an infrastructure for checkpointing applications, and a “resurrection” server that acts as a configurable watchdog service for the entire software stack from device drivers to web servers.
The real goal of the microkernel architecture is to make these watchdog services as reliable as possible (there's only a few thousand lines of heavily audited code running beneath them). That, combined with user-space device drivers (so faulty hardware or driver code doesn't bring down the whole system) would address most of your concerns.
No surprise, that's the path they are headed down. I even see that this release includes a "block device fault injection driver" for simulating hardware failures.
