The GW cadian sprue comes with the bits to make a sgt (pistol and chainsword), and a number of riflemen. Now some of these riflemen can be given alternative weapons (Flamer, GL, Melta gun and plasma gun - the melta and plasma you had to buy aftermarket, but hey, who cared ?)
When I put the DKK together I ended up with enough to equip each squad with one of each. The cadians have one of each.
When I play Dawn of War (WH40K on the PC), you can give each squad three weapon upgrades (but no heavy weapon option, so maybe they had spotted what I later learned).
Using Army Builder, the IG squads (including Defenders of Vraks (the Bloodcoats) and the Servants of Slaughter (the Tigers)) can only be given one of these weapons (and a crew served heavy weapon, but that doesn't enter to this at the moment). The awkward thing is that I have modelled all of the squads for the DKK, Cadians, Bloodcoats & Tigers with all four weapons. So including the Sgt, there are only actually five riflemen in each squad for all of these armies.
I'm gonna fudge this. Stand by for a house rule:
If both opposing sides have modelled weapons that do not appear on their Army List; as long as it is identical to their opponent's not accounted for weapon; these identical weapons can be 'traded off' against each other on a like for like basis. This can only apply to armies written using the same basic codex (ie, derivitives of the IG).