Since you're working on your own thing that may or may not be like a traditional Forth at all, and also mention Uxn, you might find some ideas in Ben Bridle's Bedrock worth stealing:

https://benbridle.com/projects/bedrock

In particular the reasoning for what he changed compared to Uxn might be insightful:

https://benbridle.com/articles/bedrock-differences-from-uxn