Originally Posted by Jephie
I'd like a phone that is...
The size of an HTC Desire X (118.5 x 62.3 mm), at most Redmi 3 (139.3 x 69.6). Thickness is not much of a problem, but my hands and pockets are not that big for the length of 'em. 15+ cm long is just unwieldy, I tried, but couldn't get used to Motorola E5.
One that keeps the battery like Nokia 1100 (a week or two standby, a few days with occasional use. 5 days of standby, at least? I tend to lose it when the battery runs out!).
One that has slots for 2 at-least-3G SIM cards that both work on at-least-3G at once (Redmi 3, say, is officially "3G dual-sim", but if both are 3G, one of them is relegated to 2G anyway). I don't expect to use Internet much, so Dual Standby is good enough.
A third, separate, slot for an SD-card. Although, OK, 128 GB is half my computer's hard drive, so built-in 128+ storage will do in a pinch.
Frequencies: one SIM is currently Australian Optus (3G 900MHZ, 2100MHZ; LTE Bands 1, 3, 7, 28, 40), the other is Australian Telstra (3G 850MHz, 2100MHz; Bands 1, 3, 7, 8, 28) though just one of the two will do. If the hardware is right, I don't even mind moving to Vodafone (3G 850MHz, 900MHz, 2100MHz (being refarmed as 4G); LTE Bands 3, 5, 1).
3.5 headphone jack necessary, at least 3 hardware buttons on front very much preferred (I'm not even daring to hope for a non-touch keyboard, but the more hardware buttons available, the better), GPS handy, radio welcome, a 4+ MP camera will probably be there in any case.
Solid build preferred, though, as you say, cases can compensate for it.
Rooting ability. Inability to just copy files for a backup drives my inner Linux user crazy.
A relatively small, solid, long-battery-life phone that's not used often, but expected to be up to the task when it is needed. Is that too much to ask?
Well, go with Huawei Y6 Pro. Unlock bootloader, get stock ROM, using spflash tool flash patched boot image to get magisk root. Also, about that battery life expectancy. Let's be real. If you aren't going to install any power hungry app, like email or a browser or social apps, not going to have the phone connected all time to wifi or data connection, brightness and battery saving to max/ultra, you might reach around those 5 days. But you would literally not be using the smartphone. Tech reviewers are amazed by a 3 day standby phone and you want 2 weeks? Don't expect gaming on this.
[UPDATE] Took another look at your request, I am also suggesting Samsung Galaxy S5 Mini. Seems some people found out that there are extended battery packs for it, going up to 8500 mah. Sure, it's a brick afterwards. Don't know, didn't dig enough in those forums. Also, you get custom roms with pie, which is known for better battery management. Also, if you plan on getting more battery life, use lite versions of those apps and consider underclocking +/- undervolting.