Hi, @SlimJ87D - Sure, I tried running stock OOS 4.0.3 on my phone before trying anything else. My wife's phone. too. I even waited a few days, just to get a clear picture. The standby battery drain was really bad on both.
Thus, this thread. I'm an engineer, and I'm a firm believer in the Scientific Method. I change one variable, and measure the results to see if there is any resulting effect. That's generally what I have been doing. This thread has been running for a few weeks now, so I have had a lot of time to try stuff out.
So far, the best I have seen for standby battery has been with FreedomOS 1.3, and a very minimal installation. For example, here is all I had installed when I started taking readings:

Things were looking more promising after the install. Here is a screenshot from last night's battery drain:
Things were looking more promising after the install. Here is a screenshot from last night's battery drain:

Before installing Freedom OS, my battery drain would have been about 4% for the time shown, and now I am seeing 1% over 4 hours. That's the best I have seen on the OP3T so far.
I have started to - slowly - add some of my usual apps back into the mix, staying away from any apps that use the internet at this point. None of those apps have noticeably impacted my standby drain.
So, I took made a TWRP backup to have a good baseline to return to for future testing.
After that TWRP backup, I installed Franco Kernel r12.
For the first time, I saw standby currents as low as -11 mA, and sometimes extended stretches of -18 mA.
While I have cut back a lot of functionality that I need to slowly bring back to the mix, I'm feeling more hopeful about things now.