Ex-S is the enhanced version of the S-Gundam, from the Gundam Sentinel story. I’m going to TL;DR and refer to the Gundam wikia for the details of the story and Ex-S.
The original MG Ex-S was a bold move by Bandai, but the execution left something to be desired, especially when they released it in 2011. However I chanced upon some styrene conversion kits by Lemi, which was cheap enough for me to give it a shot. The kit contains new shoulders, extensions to the beam smart gun, chest and knee armor. I haven’t seen someone build it but they looked detailed enough to make a difference.
In the end I think they made a pretty substantial difference. In addition to the added details, the larger shoulders beefed up Ex-S substantially. The lengthened and detailed smartgun is now more menancing. Finally the extended chest armor gave more volume to the suit. Win win win!
There are two paint schemes with Ex-S, I chose the version dominated by blue, with a 2-tone camo. The other version was the original MG’s with the standard Gundam red shoes and various armor pieces. I also did a modernized 2-tone white for it as well.
I also added a pair of movable-finger hands for it to “grab” the smartgun. The fit of the Lemi pieces were fine, but you need to test fit carefully. Overall Ex-S was quite a bit of work painting and decaling, but I’m happy to have a heavy Ex-S of my own.