Re: And therein lies the problem ...
Huh. I haven't used a Sony, so I can't rightly say on the specific behavior of whatever blend of hardware and software they have going there, just the stuff you already covered about manufacturers and carriers layering it on. If it's a known issue with them, ok. I recall we had something about the camera API would get stuck continuously doing a CPU wakeup and sucking battery down, needing a power reset to fix. That was 4.3.something though, I think.
I'm on 5.1 at the moment, and was evidently wrong about battery use. It's saying 5% (left High Accuracy on evidently). That reminds me, the Battery percentages don't add to 100% OR to the percentage used. I nasty-grammed them about that once, need to do it again... Oh! Are you using the new stuff like Trusted Face and Trusted Place? Those seemed to drain it faster for me and didn't really give me much benefit, so turned them off again. Those might hold the camera and location services at the ready.
Nope, don't work for Google, be an interesting workplace to have if I did. I just got tired of the same nonremoveable bloatware you touched on after having a Samsung Epic and Galaxy Nexus, didn't want to have to root my phone in order to strip down to the standard stuff. So I yoinked an N5 off the Play Store when they came out. This probably makes me part of like... 2% or something, to be consistent. :)