If you want to make a army that uses tyrannic war veterans then your only choice is to go with the ultramarines. They are the only ones who can take the tyrannic war veterans.
Actually you don't. By doing that you miss out on their special rule that allows them to attack infantry with krak grenades.Lord Malachi said:You can make the equivilent of Tyrannic War vets by using traits. Trust your battle brothers and Suffer not the Alien to live give you all the same benefits, although it costs a few points more. The bonus is that you can give it to any squad you want and thereby field more than just three units. To get Hellfire ammo you just need to throw in a Deathwatch marine. The Deathwatch HB is way better anyway. I think doing this in a DIY chapter is much more interesting than going Ultramarine.