I have done this. I think the issue is it started to get complicated. You have a wider range of places, intensities to dial in. It's totally possible with lactate testing etc, but then you also have the fact it becomes less plug and play where you just do your training and forget about it.
I also noticed no difference, going from vanilla, to playing around with it and back to vanilla. The amount of expected to improvement based on load and sirpoc guidelines, was the same anyway.
I think here's a clear pattern, the guys who have had best success like this have kept it vanilla. That isn't to say another approach can't work, but you risk changing stuff for the sake of it or hitting the wrong intensities by mistake and drifting away from the idea of the training. You then also have the fact of how long can you sustain it for, how much have we changed the mechanical stresses? That is a huge factor overlooked my some.
I actually firmly put myself in the camp of "I can make this better". Then quickly found out, I probably can't. Or at least there's not the body of evidence to say there's huge value in playing around with the balance. I think that's the incredible part of this. We haven't really shifted too much from the original goal posts, over two years ago. Just about everyone with an ego has come along, including me and said this is how you make it better. But, never actually provided hard evidence.
I really love the debate though, it's all quite interesting. But even you have Bakken basically saying for hobby joggers, sirpoc has basically cracked it.
I do however, change my views when you have probably maxed out what you can do on vanilla. That is a different scenario. Totally. But, other than sirpoc graduating his own system, there's barely anyone else who has reached that point. Seemingly, he's already working on the next level, or what to do next on hobby hours - as you have quite a jump I feel to basically training like Bakken. So he's at the grey area in-between.
Just my feelings, long time reader and felt I would just dish up my thoughts.