Sorry if you get this twice my email server's acting up 
I think.
 
As someone sugested 
that the intructions be changed a little. I would totally agree. You can even 
add more instructions. For example I am currently working on a core in verilog 
which is similar to that of the HP calculator's processor but after careful 
thought I reorganized all opcodes and now there is no backwards compatibility 
but you can recompile anything for this since the instruction set symbolicly is 
identical. You could even write a code converter to change MIPS opcodes to your 
nonstandard opcodes. Even a runtime converter(Just watch out for transmeta's 
code morphing patents).
 
Ali
P.S. Anyone who 
wanted to use your core could always redesign the decoder to make it compatible. 
All you need to do is change like two instructions and they should not be able 
to stop you legally as long as you do not infringe on any of there other 
patents.
 
P.P.S. Any companies 
reading this I would really like a scholarship for college, I'm in high school. 
;)