Thanks for the Lintalist recommendation. It looks like a well-rounded project and a good productivity booster for folks who are proficient with AHK.
I personally have gone down the Python route for this kind of thing.
For example, I actually have something substantially similar to Lintalist, worked out with YAML/JINJA2/TK.
I do see Lintalist appears to have some distinct advantages in some areas, relative to Python. For example, it is obviously geared toward simpler manipulation of WindowsAPI primitives, which can definitely require a lot more grunt-work from within Python.
In contrast, with Python, there is very little (if anything) that cannot be tweaked to your exact liking. Packages exist for everything under the sun, and you can configure things down to what precise syntax you want to use for snippet placeholders (for example), and what kind of expressions or dynamic values you want to have available to populate them.
This is why pastefromfile in FARR would round things out nicely, since it would permit any kind of inter-process communication where simple textfiles serve as the "pipes" between different applications, and FARR could serve as the general-purpose GUI front-end. Technically, it is already possible, since FARR is so extensible, but one goal is to minimize the amount of "clever workarounds" required.
Anyway, it is always satisfying to see other people's solutions and tools for productivity boosts, all centered around great ideas that you know took some time and thought.
Thanks, therefore, for your time and thought, and informative feedback!