Look, I have no issues rendering global tone, color and saturation (among other things) from Raw to produce the color appearance I want to represent.
To me, saturation/vibrance is not something I want to work with globally, without some control over how it's applied. But if you're happy with a single global control, by all means keep using it.
I don't need to use a blend if and jump through all kinds of hoops. Just because you have layers, blend modes and so forth, doesn't mean you have to go through a 38 step, convoluted process. You might, it may be 3 steps but as yet, I haven't found the need. I like to practice KISS.
You're making it sound so complicated, but it's not. I have a few actions I use as a starting point, so it's just a click or two, then I can fine-tune from there if I want. But I'm not a wedding/event/sports photograph who needs to process thousands of images a week, either. If I were, maybe I'd just stick with the controls in Lightroom. But I tend to put a little more time into my images and I'm perfectly content to do so. Lab is a very useful tool in my toolbox, and a few extra clicks to do the conversion is a complete non-issue from a workflow standpoint.
There's no reason to sharpen the L channel either, another exercise in time loss and data loss. Just run the sharpening and fade luminosity. Is it 100% identical? No but it addresses the problem you're going after in Lab, color fringing. Its faster, it causes a lot less data loss AND you have the opacity slider to boot
I said point-blank in my first post that I wouldn't make the trip to Lab just
for sharpening. But if I'm going to Lab anyway, I do my sharpening there. Data loss from Lab conversion is a non-issue for 16-bit images, and since I sharpen a duplicate layer I have the same opacity/masking/blend-if options as your luminosity blend mode in RGB.
Lab has a role in image processing. But as I said, its recently become the big macho color space for doing anything and everything according to Dan. If he would spend just a little time looking at Raw rendering (instead of slamming it or trying to teach how to polish turds using Photoshop), his ideas might be easier to swallow. He sees everything from the perspective of a hammer in which every image correction (NOT rendering) is a nail.
I'm not a Dan disciple, I disgree with him on things like 16-bit, wide-gamut, etc. And I agree that a lot of the stuff in later sections of his Lab book a bit silly and does seem to involve polishing turds. However I do find the techniques in the early chapters very useful.
It sure seems like your position on Lab is at least partly tied into your personal dislike of Dan.