Java Bytecode to Assembly Code: Practicality?

OK, I was back home for the holidays and was fortunate to talk to a programmer working at NASA's Jet Propulsion Lab. We were talking about using assembly code when memory space is precious.

I asked him "Why not code in Java bytecode by hand (as opposed to having Java code compiled to it), then use the GNU Java Compiler to translate it to whatever machine you need?"

I've been thinking about that for a long time now and I'm curious: is this a practical idea at all? If so, why don't people do it?

Cheers!

It's easier to do it in C and then compile it for the architecture you need. Why go to all the trouble of creating Java bytecode by hand and compile it..

If done properly C is pretty source compatible between architectures. Just look at the linux kernel and the BSD sources.