Apologies if this is not the right place to ask this, but I feel that an audience who jailbreaks may know the answer to this.
I am trying to hack files right now to change my region settings exactly how I want them on iOS, hopefully being able to sideload it somehow without jailbreaking. In effect, I want the US region still set with the ability to keep News, Apple Pay, etc. with everything as-is on the US region except for date formatting. Right now I am on Singapore, since I write dates as day-month-year.
A few examples are necessary since other region formats have leading zeros, don't use slashes, write years as two digits only, or have other oddities compared to simply switching the number placements from US conventions. Using today's date as an example:
8/9/2018 (in short form with no leading zeros)
8 September 2018 (in longer form again with no leading zeros)
Saturday, 8 September 2018 (the longest form with weekday added)
Singapore is the only region that currently works for me, as it
Keeps AM/PM spaced and capitalized how I want (for example, 8:31 PM).
Uses $ as the currency symbol.
Keeps English number format convention, e.g. 1,234.56.
Those can be viewed in Settings > General > Language & Region. However, there are some undocumented changes that occur if the region is changed. The following is not exhaustive but gives things that I have noticed in a few days' worth of typical use:
My Google searches redirect to Google.com.sg (for Singapore) rather than staying on Google.com. This would be fine if I were there, but I'd prefer for it to use regular Google. (I can't find a way to change this; however, in the past when set to US as the region, it would automatically be overridden if I were connected to the internet via a foreign IP.)
The News app is completely gone. A widget remains accessible from the home screen, but it only shows news articles from channelnewsasia.com which I have no desire to read.
Google Maps defaults to metric measurements. (I can change this in its settings and also don't have a problem with it as it forces me to internalize them, but I would prefer it be in imperial units just in case other apps are expecting it for some reason.)
The holidays available in the default Calendar app show as those in Singapore, not US holidays. (This is probably a non-issue as I don't use Calendar much.)
It is bugging me a bit that iOS is intentionally nerfed this way to force you to conform to (any country's) standards when Windows has a simple dialog box that can basically change exactly what I want without affecting anything else. (I think macOS also offers something like this.) If anyone can offer suggestions as to what file or files to edit to modify the region settings, or if anyone knows of a jailbreak utility to do it, that would be very appreciated. I have access to an iOS 10 IPSW that is currently extracted, but searching through every file for relevant strings has been fruitless (no pun intended).
Please do note that I am looking to tweak this on the system level and not just in the status bar or anything else, for example. This should be able to tie into the settings in Language & Region, modifying one that already exists.