Some suggestions for really nice GUN packages, which Ubisoft could sell:

G.I. Set (Thompson M1A1, BAR, M3A1, .30 M1 Carabine etc.). These weapons were supplied to Bolivia after WW2 in it struggle against Communists. So likely to be found there.
Axes Set (MG42, MP40, StG.44, FG42, etc.) As you tell in your storyline, Germans ran to Bolivia after WW2. So you could make it likely to have those weapons there.
Vietnam War Set (M16A1, XM177, M79, M60, Swedish K, etc). Bolivia struggled in the 1960s and 1970s against communists and were supplied with these same weapons by the US.
Cuban Set (PPSh-41, FN-FAL, AR-10, PPS, AK-47 etc.). These are accurate weapons used by the ELN Ejército de Liberación Nacional de Bolivia, made up by Cubans and Bolivians in the 1960s and combated by the Bolivian Army and American forces in those days. It would make a realistic set.

I have bought the Bren gun set already. I don't like it, that I cannot put a skinn on it, so if you add new buyables.... please don't make them so, that you can't adapt them.

Gun sets are GUN SETS so LEAVE the Skins, Uniforms and other JUNK out of the sets. At least FIVE guns per set. I am not buying sets again, with 80% skins, helmets and other garbage in it (sorry for my wording). Your price of about seven Euro per set, as it currently is, is reasonable. I would not pay more for it though (per five or six guns).

Thanks