Alternate versions of Darth Vader are nothing new. A casual browse of the internet will reveal no small number, varying in style and quality. This is my attempt at giving the Sith Lord a mobile suit and, to be honest, there are a few Gundam fans out there who have already made one for Vader.
One of the difficulties in designing a mobile suit for Vader is that his suit/costume is somewhat plain (by mecha anime standards), thereby not giving much to adapt. The other difficulty is that his two arguably standout features, his helmet and shoulder guards, are not consistent to the form of a typical mobile suit. In other words, a design which is still recognizable as Vader may not quite look like a Gundam unit and vice versa.
Vader’s helmet is presumably inspired by the WWII-era Wehrmacht design. It is also consistent to a 5th-century Japanese Kabuto. Both designs have a long skirt which protects the neck and covers all but the face. So, unlike typical Gundam, I have mostly kept this. And in place of a mobile suit’s face-guard is Vader’s respirtory filter. A typical mobile suit design also includes some sort of “crown”, something which Vader does not have. Here I have included it anyway which, surprisingly, does not entirely clash.
For the shoulder guards, instead of the sharp form commonly found in Gundam, I have simply adapted Vader’s striped design as is. I have maintained its relatively smooth and blunt form but exaggerated its proportions.
The so-called backpack is something I can take liberties with. Wings and/or winglets are common in Gundam and can easily be viewed as a cape. However, so many wing configurations have been done in Gundam that I cannot think of anything original which is also aesthetically pleasing. Instead, I have opted for prominent boosters inspired by the form of a TIE Advanced along with a few winglets. Even this is not particularly original but I am happy enough with it.
And yes, he is carrying extra light sabers in case he wants to throw them.