Well, either your Noggit will start crashing, or will not. Probably will. If you want to use Cata+ models in Noggit, you need to retro-port them to WotLK. Check retro-porting section for this. Adspartan has a nice convertor.
Anyway, don't put anything into original MPQs, if thats what you wanted to do. Just create a new patch, name it for example patch-4 or patch-w or whatever and add all stuff into it. If WMOs will crash Noggit, which is likely to happen, well, then you can't, not without using Adspartan's convertor on them.