The Fenrir II may have replaced the Fenrir in the quartermaster's orders and in general production, but they still had a bunch of old Fenrir kicking around . . . and with all the usual RATs provisions . . .
Between ER3145 and FM3145 (ER Dark Ages is notably missing a BA RAT), the Lyrans have a lot of old Infiltrator Mk Is still and IS Std as about the only FS stuff available- though I lumped in clones which would be Cavaliers and salvaged Raidens as a possibility. FM gives them a chance at GDL Stds, but that has to be old stock since the Falcons have controlled the factory on Glengarry since early in the Desant (late 3134) so those are no in the pipeline. The GDL Infiltrator is since it is built on Furillo. The majority of the Lyran BA corp could be said to be made up of Night Hawk XXI, Smoothdavid III, GDL Scout, Infiltrator Mk I, GDL Infiltrator, Rottweiler, IS Std & clones, Fenrir, GDL Std, Fenrir II, GDL Heavy, GDL Strike, and Sloth. They probably have a sprinkling of suits salvaged from neighbors or during the Jihad (Phalanx?) along with purchases of things like the Clan Med BA Rabid/Volk/Bar, Black Wolf, Cuchus, and anything else bought from the Foxes in betters days. But by 3145-50, IMO their BA formations would be as chewed up as the mech formations- might be why the Fenrir came back to prominence, got dusted off in the warehouse- and its going to be about what gets produced on their remaining worlds.
And for all that, I do not worry about quads (which seems to be the Lyran BA motif) like I do medium troopers who can do leg attacks.
So with the Flam D being two Plasma Rifles, I would say it was to face the Republic- who has a nastier BA corp when it comes to gear and is more combined arms IMO.
But . . . like the Wulfen, what about the Black Wolf- designed/built 3142 and set to use IS Mortars and Support PPCs.