TBH if I do end up replacing it with something else, it doesn't have to be stock Android or even a powerful device. I'm okay with replacing my 4a with some cheap ultra-budget shanzhai phone as long as it's small and it works with T-Mobile US's LTE network.
Also the iPhone Mini itself isn't an option—not only do I not want to be part of Apple's ecosystem, but I have sensory issues and can't handle metal phones. I need a plastic phone. And no, a case isn't an option because a case would just make the phone too wide for me to hold.
Going back yo the previous OS would fix that, but it was also buggy and missing proper support for the new gesture navigation. I love the phone but it also makes me hate Google so much.
At this point I think I'm just done with Google's Android and I think I'm ready to try one of those Chinese forks with a super-colorful iOS-like UX.