Hi Brad, welcome! Glad you found the forum--it's not advertised much, and Ren-C keeps a low profile. (It's enough trouble supporting just a couple of customers in the face of the desire to keep evolving the language!) So only a particular kind of person fits...seems you fit!
I am a big fan of Haskell, and if I didn't think that paradigm was already saturated I'd probably be more involved there. Here there's some fun in being able to still invent at the level of undiscovered fundamentals.
Hopefully you've seen "A Justification of Generalized Isotopes", as that is one of the biggest outcomes of that exploration. I always disliked the /ONLY refinement, and it took a long while to get to the right infrastructure to see how a lot of different problems could be seen as instances of the same problem. "There needs to be a quoting level of negative one" took a lot of steps to get to.
Binding remains the biggest open topic for me, and I'm glad you want to talk about it!
The Red/System dialect is neat. Long term, it would be cool if that was used to implement Ren-C instead of C. It's one reason why I've been careful about the usage of C++ features.
But Red (and historical Rebol) have always tended to code up simple cases, then call it a day and move on. They don't throw hardballs, and when you do so, the lack of composability becomes obvious. I'm trying to maintain the spirit of the design while still attacking those bigger issues.