The generation of code from the protocol description isn't driven by a
fear of the efficiency of Lua. It's driven by the fact that I don't
think Lua is going to be running on a 8-bit Freescale HCS08
microcontroller running at 24MHz anytime soon. And the larger
platform the C code targets is a ColdFire that has about 16k of RAM
left over and about twice that in ROM. Yes, I'm one of those embedded
systems guys who hangs out in this mailing list to remind everyone
that while Lua can go lots of places, it can't go everywhere.
Those are a little small for embedded Lua, but I think the ColdFire is well within the realm of possibility. But, you're right, native code is still your best bet for those two. I'm an embedded systems guy as well, and I've used eLua previously. I assume you've read this thread about eLua on a ColdFire?
FWIW, I have embedded Lua into a ColdFire. The product ran four Lua instances under separate MicroC-OS tasks. It worked quite well, but we did have to be careful on memory usage – I believe the whole system had 512K RAM available.