This was fun. Here is my submission. 

Wasn't much to change tbh, Just a few macros changed as methods and "DEFINE FIELD" syntax to be modified with cl_abap_datadescr.I actually gave up but was bored at work so thought to work with ChatGPT and made the changes. 

Adding the link here for referencehttps://github.com/sbcgua/abap_mustache/tree/steampunk

Hi Mamikee, Added my code zcl_scc0523_mustache_app to the same repo.Below is the test result 

Saw this very late after making all the changes. Thanks for sharing this