-> make a toy-subset of C to mips compiler
gcc -mmips -> make a toy-subset of java to mips compiler
Waste of time, java is shit. -> make a toy language to mips compiler
Depends on how complex you make the language.
Making your own toy language is the funniest option since you make it like you like it. Start simple and branch out.
If you keep it simple then converting to asm will be very easy.