Robin2: Making the compiler might not be monumentally difficult if you create a program to translate your code into C/C++ that could be processed by the Arduino IDE.
That is definitely one way of doing it, plus the Arduino IDE would also take care of all the other parts of the toolchain. Since it accepts pure C/C++ - the compiler will just need to generate the code which fits with the setup / loop routines. This way would also be easiest for people who don't already have the Arduino IDE installed
[EDIT] Sorry, I think there might be a confusion here, when I say 'compile' I actually mean transpile the language to C/C++ and then just use either Arduino IDE or avr-gcc directly to compile it to machine code. Writing my own compiler for avr would be crazy, I agree :)
Delta_G: Syntax is the easy part. Anyone can learn the syntax. The hard part about programming is the logic and that's the same in any language.
I disagree, syntax has major effect on how easy it is to understand the code, plus syntax is not everything, the way language is structured is very important as well. Compare C to x86 Assembler for example.