These are minor modifications. There is a second sergeant on the GW website, but he's no longer listed for sale. I'll be searching for him. The figure on the left has a different sword from a Reaper weapons pack. The one on the right has a gun replacement. These aren't big changes, but they're something. The Reaper packs have a variety of swords, but I think this is the only one different enough to use.
I went ahead and ordered some Forge World figures for the first time today. These will add some character to the squads:
The 3 man sniper team will be split up into three different squads for a little uniqueness. The lascannon team will also break up some of the monotony, since I've got 5 total in the army.