Accelerator boards - no future? Bad business?

[Swift Griggs]

Remember all the accelerator boards for the Mac, Amiga, and even PCs in the
90's ?  I've often wished that I could get something similar on my older SGI
systems.  For example, fitting an R16k into an O2 or doing dynamic
translation on a 4.0Ghz i7. 

I'm most familiar with the Amiga accelerators.  I suspect those who
produced them were helped out greatly by a couple of factors.  One is that
the hardware specs were very well known and full schematics were available
for most (all?) Amigas.  I doubt the same is true of SGI machines.  The
other is that many Amigas had processor "slots" (with edge connectors)
rather than some tiny fiddly ball-grid array etc...  but I'm not a EE; so
maybe that's bunk.

When I look at these boards they seem like they'd be a LOT of work to
develop and produce.  I wonder how they were even economical to make back in
the day.  Plus, now the user base will probably only shrink.  It's not a
great business model for a hard-to-produce item.  It doesn't keep my
techno-lust from wanting it, though.

So, here's the question. Is my dream likely to ever be possible enough that
a boutique shop could pull it off and not lose their shirt on the production
costs and R&D to do it ? I'm encouraged by things floppy emulators that are
produced for these old machines. However, that's probably significantly
easier to make than a CPU accel board. 

What do you guys think?

-Swift