Okay - so here's the way I would do it, given resources, time, talent and so
forth:

<talking through my hat>

Start by duplicating the basic VAX processor in a single chip, as discussed
here.  Build the Memory Management unit to run current-tech PC100 SDRAM, or
an interface between the SDRAM and MMU.  This may go on the main chip, or a
second chip.  Clock the whole thing at some multiple of 100Mhz.

Second - build a MSCP-emulator in chip #2 that interfaces to SCSI.

Third (optional) now that we understand MSCP, build another chip that
interfaces MSCP to EIDE (because the drives are so cheap).

Fourth - 10/100BaseT interface - again, backward compatible to common DEC
equipment (DEQNA?) (DELQNA?)

Fifth, and last - build a chip for QBUS interface.

Now take these four (five?) chips, drop them all on a QBus board with as
many RAM slots as you can fit.

Voi-LA!  A single-board upgrade for most (any?) QBus-based VAXen, with SCSI,
Network, and high-speed RAM all unfettered by QBus limitations.  QBus is
still there for all your older peripherals.

Once this is working, build a new chip for each of the other popular VAX
busses (VAXBI?), and build a similar single-board replacement for those
architectures.  Also look at board replacements for the littler machines,
such as VaxStation2000, 3xxx, 4xxx, etc.

</talking through my hat>

The sad part is, although I love the VAXen - I don't know enough to know if
what I just lined out is even remotely practical, possible, or even if it
makes any sense at all.

I just think it would be cool!  Imagine - 1GHz VAX 11/7[58]0 single-board
replacement for almost anything out there - RAM up to 1Gbyte (can this
architecture address that?), etc.

Can you *imagine* NetBSD on something like that?

Scott