Sadly, I don't have the Extreme Burst version, only the regular Master Grade, so I have no idea regarding the Wings of Light. But how exactly is it difficult to put them on, aren't they just one solid peace?
As for the knees, it's rather strange. I've never heard of a Master Grade kit which had so much trouble with double-jointed legs. Well, there's kits that have limited articulation range due to the armor plates applied, but the upper knee joint won't even more an inch if it's just the inner frame! I seriously fear that I'll break the other knee as well if I force it more than I already have.
Oh, another thing: How the hell did you get yours to hold the Arondight with it's LEFT hand? The only way I get the kit to hold that big, heavy sword is by using the closed right fist it came with.
And just for aesthetic means, if I were you, I'd split it's legs more, so it looks more like in the anime sequence.
The Wings of Light are one solid piece, yeah. But it's getting them into the Wing piece that can be challenging. You have to put it in perfectly then fiddle with it a bit to get it to look correctly and not bend. The Wings of Light alone took me an hour or more to do.
As for the knees, yeah I kinda found that weird as well. I've never had any other issues with that before. Hell, sometimes most of the knees are too loose. Heh, the simplest Gundam Models are usually the best in terms of standing up.
As for the Arondight, I'm not sure about the regular Master Grade, but the Extreme Burst one's hands have a little bump on the palm to help hold the sword. Mind you, it wasn't easy. Swords never are actually. Although, neither are guns sometimes too!
As for the pose, it's suppose to be in the dashing forward pose more than the one you posted. I have to adjust the sword a bit more I think to get that proper pose. LoL, at 4AM, I wasn't quite in the mood to fiddle with it.
Next up, the Infinite Justice. I'll probably do that tomorrow.