This is really awesome! I've had some issues with a handful of legion wmos that I've tried retro-porting. First off, some WMOs from legion have an issue with windows 10 users when ported to WoD, thankfully, this issue is resolved when those wmos are then ported to WotLK (they still work on WoD even after being further retro-ported). However, I have another issue where regardless of how they're ported, some WMOs will cause your standard fatal error. An example being World\wmo\brokenisles\suramar\7sr_suramarraid_exterior.wmo. I can only assume that this has some extra data that didn't get removed. I'm racking my brain over this- but I'm not seeing anything like extra chunks in either the root or group files. I'll keep looking, but I figured I'd aught to make a post about it.
Update: I tried loading in the wmo without porting it all! It works, but of course, has the texture bug. I might just have to fix it by hand. Joy.