We are told that grenadier units are split up amongst the more common-or-garden Iggies. But that they come from proper formed units etc.
So, I have a desire (and the figures) to field a grenadier platoon. Of Pl HQ and four squads.
So with an army list that already includes two common-or-garden platoons (of HQ and four squads), I could possibly fit in four Vet Squads to represent the four squads of the Grenadier Platoon (there is no codex entry for Grenadier Platoon HQs).