Slider flex cable again?
Anyway, only way that i found that can be used for answering/ending calls is xposed module called "xposed additions". Very few options in it, but it can bound any key to be used as answering key.
It is working on stock rom, with xposed framework for GB installed.
You can find apk of it in http://forum.xda-developers.com/showpost.php?p=44034334
and actual module you can download from XF app itself (you only need root, but that is pritty much easy these days)
Only down-side is that front buttons can't wake device, only power button. But since you unlock by sliding out, it won't affect you. I personaly have search key enabled for calls, but even home or menu key can be used.
Also, check keyboard at
You can use it for texting. It will be slow, but better then nothing
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