Thanks again Hunter, I'm glad to be clear of that first hurdle.
Oooh, this is a really cool idea.
The mix of parts is really working well here, but to me there's something about the arms that somehow feel more 'off' here. I think it might be the hands. Consider using the MG hands on the HGUC forearms (Or the SD's, I don't know what those look like)? I think that might level things out.
If you wanna go crazy you can put the MG's giant beam saber handles on the HGUC backpack 
Thanks for the advice Sharkdog, I would up taking all of it. I spent the weekend at another con with the model club and left it on display as a wip. Lots of people commented on it, and some people asked me where they could buy
the kit 
But spending so much time looking at it, I decided to put in the HGUC backpack again. Then for giggles I put in the MG beam sabers, and I actually like how it turned out. I was on the fence about the MG hands, mostly because the MG ZZ hands aren't very good. It could have gone either way, but I figured if the MG beam sabers are going to be on it, then it will need the bigger hands to wield them!
Here it is with HGUC backpack, MG beam sabers and MG hands. I also added the shoulder-vent-things from the HGUC, and the front red cockpit hatch piece from the HGUC. Instead of using the whole MG front skirt I also put in just the protruding parts from it. I'm excited that so much detail is going into it successfully, and I'll need to find some better replacement MG hands for it.
I contemplated adding the 1/144 FAZZ beam cannon, but in the end I decided that it is a ZZ and not a FAZZ, so that didn't make sense. However, I think it could use a weapon...
Conceptually, I think I am going to build a junkyard themed base for it. Judau, the ZZ pilot started out as a junkyard MS scrapper before being a pilot, and then also since this kit is made up of other kits the junkyard idea works again.
Slow progress, but lots of hmmm-ing and haaa-ing.
