It's not "oh no, terrible idea"...so I'll take it. 
I have thought about how this would affect teaching the language.
If you think of it like learning there are "normal" parameters, and then learning "quoted" parameters is part of the whole power to make things bend.... then you might imagine a certain style of teaching where people think for a while that things like APPEND are somehow "keywords" and then they have to use slashes for their "functions".
But then...you reveal... that /FOO: is the magic "keyword-making tool", and they see it as a choice.
Perhaps people would start thinking of these as being in different categories--and using a mix of both. ("I use FOO: for functions, and /FOO: for keywords") But that starts to make you wonder about what to do when they slip up... and what they thought was going to act as a keyword falls through the cracks as a discarded value.
(I've written a bit of theory on how we might do a better job of "noticing discarded values", and there actually are probably a few new tools for us here... but... nothing imminent.)
Anyway... who knows. Maybe this idea of "there are functions you call with a notation, and there are keywords" isn't such a bad idea. It's how other languages work. 
Perhaps some users would find comfort in drawing a distinction about which words they "activated".
Ultimately Redbols have brought in the dangerous opportunity that any word you are looking at can be redefined, and might call a function.
Yet we have to write code, and meta-code, and meta-meta-code, etc. in such an environment.
So I would say your intuition is correct--this is like noise shaping in engineering--where you try to push the system-intrinsic noise into places it won't matter (like moving sound noise power to where the human ear won't pick it up). We cannot remove the complexity, only push it other places.
But I feel that this pushes the concerns up the spectrum to the meta and meta-meta code, which already had to be careful anyway. And I don't think any of that code gets too much more complex...just a bit different.
I think it will give people a better grounding to be able to use the language enough to even care about what's in play at the meta and meta-meta levels...!