I saw this basic cross-compiler on YouTube "8-bit Show and Tell 2". This is a cool project and I was curious what others thought about it, especially regarding the possibility of getting it to work with the X16. It looks like some of the memory locations are configurable but not all based on what I was reading. There is a github page with source and they are looking for contributors. It looks like some of the code is written in D (https://dlang.org/) and some in Assembly.
It may also be possible to use this project as a guide for developing a similar branch/offshoot for something a little more tailored to the X16. The cross compiler is using a grammar parsing library that could be helpful for that: https://github.com/PhilippeSigaud/Pegged
https://xc-basic.net/doku.php
https://github.com/neilsf/XC-BASIC
Compiler Options: https://xc-basic.net/doku.php?id=compiler_options
Memory Layout: https://xc-basic.net/doku.php?id=memory_layout
Examples: https://xc-basic.net/doku.php?id=examples