This is a past project. I'm posting it for record-keeping purposes. Created September 2019.
I wanted to add weapons to the model even without the Fellow Booster, so I tried various things, and this is the result.
I used a Gundam Marker panel lining pen for panel lining and attached the parts directly.
I equipped the back with binders and a railgun, giving it a Hyaku Shiki-like appearance.
I could have been satisfied with this, but then I wanted a booster, so I went to the weapons shop again...

GM Intercept Custom (with additional booster) | ガッキー's Gunpla works