Moto X 5.1 VZW FXZ seems to be available :
http://www.theandroidsoul.com/download-verizon-moto-x-android-5-1-update-fxz-firmware-84184/
But I didn't succeed in extracting the system.img file.
The system.img is in that zip file from the link you've enclosed. However, when I flashed it, the phone booted up as KitKat 4.4.4 and immediately asked if I wanted to update. I almost took the bait but quickly held the power and volume down to go back into TWRP recovery. That was close, don't know what would have happened if it tried to update the bootloader with the Moto X one. Probably a nice little brick. So, I guess I'll wait for the official Droid Maxx version but it looks like if you want it, you'll have to update to the newest bootloader. I was wondering why I was unable to sideload the Moto X 5.1 Patch, kept giving me an error, it was because I wasn't on Lollipop, LOL.
Edit: Disregard, LOL, I think I grab the wrong files. I updated my Moto X DE to LP 5.1 via OTA the other day, but RSD back to stock before and I think I just flashed those files instead. I've been drinking..... let me try again.. LOL
Edit2: Ok, now I know what you are talking about. Tried to mfastboot system.img and it is saying not enough space. Interesting!
Edit3: Googled it really quick, and using the -P switch it is flashing. So, mfastboot flash system system.img -P
Edit4: Still won't let me sideload the patch successfully and it is bootlooping. I'm going to flash an older modem file because I've tried to flash Moto X LP modem files before and it caused bootloops.
Edit5: Yup, flashing an older Maxx modem file worked (I flashed radio_23255.127.76.00R from VZW_XT1080_4.4.4-SU5.23). I accidentally dirty flashed the VZW LP 5.1 ROM over my Exodus 5.1.1 and it actually booted up. Everything seems to be working, just need to figure out why I couldn't sideload the patch so I can disable the extra buttons, if not, I'll use GravityBox to do it (I think it can...).
Edit6: Got the patch to flash, guess I should have read the instruction which said use the newest Ghost TWRP, I had an older version of the Obake TWRP installed. Dirty flash was a great little accident because all my apps are intact. Smart Lock was broken somewhere along the way with the newer nightly builds of Exodus was fixed by the VZW Moto X 5.1 ROM. Everything seems to run great, will report back if anything changes. Otherwise, case closed, great success!