In reply to Only a hill:
> I've often thought about the Defy+. Does it have any internal memory issues?
I never had any internal memory issues with my Defy+. I'm not sure why you think it have any? It's pretty vanilla Android once you disable the social media bloatware (as you should do in step 1). If you root it you can go further and delete the unwanted rubbish altogether using something like Titanium Backup (which does a lot more than just backups, and is one system utility app that is genuinely worth the money).
Another good thing about the Defy+ is that it has a replaceable battery, so you could take spare batteries rather than a portable power pack. I suppose the downside is that you have to power the phone off to swap the battery, and if the weather's foul you'd risk letting the wet in while you did the swap. Then again, the USB socket isn't water-resistant once you remove the rubber plug so there would be a vulnerability with the external power pack as well, and for longer.
I now use a Sony Xperia Acro S which is also water resistant. Doesn't have a replaceable battery, though.
I do think you should add a disclaimer to step 2 of your blog post along the lines of: "other launcher, GPS, mapping etc apps are available". For example, SickSky Launcher is much more compact and minimalist than Nova Launcher, which actually seems rather bloated (I've also not been overwhelmed by the author of Nova Launcher's other apps - they're OK but can be a bit clunky). I used to use SickSky's predecessor Zeam Launcher on my Defy+ and it was bulletproof. Also, some phones already have power toggles and an acceptably useful battery meter, so they wouldn't necessarily need the apps you picked for those functions anyway.
As captain paranoia says, simply putting the phone in flight mode should stop anything which needs a network connection from draining the battery. GPS still works in flight mode because it's passive (apart from the assisted GPS function, but that's not required for normal GPS to work and it isn't much use where signal is poor anyway).
Those comments apart, it's an cunning idea and well written up.