Great work on this.

Any way to get exFAT working on this? It seems to be working fine on the version from Dees_Troy (my card is formatted exFAT).

The tree Dees_Troy put up is here: https://github.com/TeamWin/android_device_htc_m8_whl (I'm sure you already know this)

I also caught him on IRC yesterday and he said he'd look at any errors in the source tomorrow, as I was having issues building with it as-is. With all the additional updates you had to make, it's no wonder!
Device 1: HTC One (M8)/831C | Hardware Version: 0005

Baseband: 1.08.20.0612_4 | PRI: 2.62_003 | PRL: 56019
Recovery: TWRP 2.7.1.0

Device 2: HTC Jewel/PJ75100 (EVO 4G LTE) | Hardware Version: 0003

Baseband: 1.13.11.1105 | PRI: 3.02_003 | PRL: 56018
Recovery: TWRP 2.7.1.0b

Device 3: HTC Shooter/PG86100 (EVO 3D) | Hardware Version: 0002
Baseband: 1.09.00.0108 | PRI: 1.55_003 | PRL: 22100
Recovery: TWRP 2.7.1.0

Device 4: HTC Supersonic/PC36100 (EVO 4G) | Hardware Version: 0004
Baseband: 2.15.00.01.15 | PRI: 2.33_003 | PRL: 40460
Recovery: TWRP 2.7.1.0