I do genuinely appreciate it you going to the effort to try this.This misses the point entirely. We are not talking about the averate bottom depth, but rather the average dive depth.
Simple example using air, calculated on a PADI eRDPML.
100 ft, NDL, 20 mins, but ascend at 15 mins to 40 ft; new NDL is 83 minutes, but stay only 80 minutes. Nice 95-minute dive, plus some ascent time and a SS.
The average depth of that dive is 50 ft ((100x15 + 40x80) /95). A single dive to 50 ft has an NDL of 80 minutes.
You cannot validly plan or execute that two-level dive using average depth.
You just won yourself one whole hour of extra bottom time because you used an average depth, and you didn't exceed the NDL permitted by the eRDPML.
That is the point I was making. No more. No less. I won't pretend planning based on average depth gives you the optimal answer, but it can give a useful answer. As I said in my earlier post, averaging a shallow-to-deep profile (especially one as extreme as 40ft to 100ft) and planning using "square tables" would not be safe - but we both know the eRDPML won't permit it either.
If I were on a boat with my PADI tables, and my eRDPML (let's pretend I own one) got splashed with seawater and wasn't working, I would happily plan that dive using the tables and average depth.