Alright, this is pretty sweet. Had the idea to do this myself at one point a long time ago, but never got around to it. Glad someone did!
You (or someone likely) actually improved my original method a bit. I never actually put the first two marker actions in my macro, only the last 4 ones. I still personally place every marker by hand that I'm using, instead of doing it in the macro. However, I'm not actually for or against it either way. I usually do tempo mapping in "sections" to help with the ad nauseam. More so, I'll do intro markers, and then go back and spam the action. Then verse, ect. Either works great though!
I can tell you up front, until using this, it does seem like a lot more work. In the end, that's not entirely wrong. If you are mapping in 4/4 and there are strong down-beat waveforms, then it's perfectly fine to use the normal method and would take a bit less time. The huge use of this comes when, as you discussed, you need to subdivide your tempo mapping for one reason or another. You can drop markers on a per-beat cycle if necessary (good for slowing down or speeding up sections); you can map on snares every 2 beats if downbeats aren't great; you can just pick whatever the hell is showing in the wave to use.
Tempo mapping a lot of Rush had huge help with this. Show Don't Tell had accents on the 16th before a downbeat. Well.... I just changed my initial tempo marker to 1/16, and then mapped using that. I would have one measure of "15/16" and another of "17/16". I've charted a lot of songs where every other* downbeat had a kick on it. I would basically be charting in cycles of 3 beats, 2 beats, and 3 beats (ie, kick, snare on 4, snare on next 2) in 4/4.
Another big help is when you have some inconsistency within a measure. I can count a lot of time I'd match up two downbeats, but see the snare hit at beat 3 falls... off. Usually due to fills being played different speeds at times. Well, just go back and rechart the measure quick with markers throughout so it lines up better, splitting the difference.
In the end, I always still try to map (even while using this method) on a measure basis. I will still map using full measure intervals, and then make the adjustments when necessary helped by this.
Can't say I fully approve of your starting tempo method, however