Question:small arms for on map artillery

[Marcello]

On map artillery has usually a rifle (or a carabine) in the second slot, with 60 ammunition points.Question for a OOB meant for release I replace said rifle with two carabines with 30 ammo points each and a pistol?
Cost point wise it seems to make almost no difference but is there some convention against that (like no rifles for trucks and such)?
This is for an hypothetical army whose doctrine emphasize artillery self defense capabilities (AP rounds issued to the howitzers, some training in antitank direct fire etc).