[Not a language designer or anything, but] I dunno, keeping some distinction between Python and the DSL seems useful, and probably makes it simpler to reason about. Too much syntactic sugar, and I can imagine it becomes easier to confuse "thing that is generating the RTL" from "the RTL".

I think of Amaranth as "a way of using Python to organize/generate/simulate RTL." Being embedded in Python is part of the utility behind it!