Regarding a potential Gallus G, I think that it could be something like the Gallus K, but probably retaining the fixed weapons of Gallus J and adding the ground use thrusters that from the MS-09G that were added to the AMX-009G, AMX-011G and AMX-101S.
Regarding the royal guard units, supposedly the Gazu L and Gazu R served at one point as the personal escorts of Haman's Qubeley, much like how these later sometimes accompany Chara's Geymalk.
Supposedly the AMX-103, AMX-104, AMX-117L, AMX-117R and IIRC even the AMX-107 (at least Glemy's prototype unit) are all classified as knight type MS.
Back to the AMX-101S, as it has been pointed out it shares the color scheme of the YMS-15E, AMX-117L, OMS-14SRF and OMS-90R. IIRC, Nee, the pilot of the blue AMX-117R, seemed to be the elder brother and essentially the leader of the two, which makes me think that his unit could technically be just using his custom color, while Lance's AMX-117L is using the generic color scheme of the royal guard members. I guess we could think of it being a similar case to Angelo's Geara Zulu and the units used by the other members of Full Frontal's royal guard.