Hobby Project: Tyrannic War Veterans

I need to get back into painting. I haven't done any since before Christmas. Best way to do this, in my experience, is to start a small, self-contained project.

So my beloved Deathwatch are going to be joined by a small training cadre of Ultramarines Tyrannic War Veterans. For those unaware, the Tyrannic War Veterans were a unit introduced in the fourth edition Space Marine Codex to represent those battle brothers who were survivors of the Tyranid invasion of Macragge. They don't really exist anymore, subsumed into the broader category of the Sternguard Veterans.

So, a few questions to answer before we begin:

How to make them?

For the base models I have a box of Sternguard Veterans; an Ultramarines Upgrade Sprue missing a few parts I used for Deathwatch Veterans; a plastic Librarian (because I think this unit needs an officer); a Venerable Dreadnought; and, these...

These are the “Alien Skull V.7 Shoulder Pads” from Plokoone's Bits on Shapeways. I love Shapeways, a 3D printing website that has so many wonderful upgrades for Space Marines that just wouldn't be worth GW's time and effort to make. Thats not a knock against GW, by the way, I have my problems with them but even I have to admit that it just isn't economically viable for them to do a wide release of Black Guard shoulder pads. They're just too obscure a chapter.

What will they count as?

The way I see it there are two choices. I can either build them as Sternguard Veterans as the start of a full-on Ultramarines detachment. With what I'm planning already I'm only one Elites choice away from a Vanguard Detachment.

Or I can make them as Deathwatch Veterans who just happen to be painted blue. It gives me a better choice of wargear and I can take them as part of the army I'll be using them with.

This will take some thinking about, to be honest.