Sentinels of Terra army building

[Shotgun Justice]

Hi all.
I've got an idea for a death watch themed marines list but haven't been able to look at the sentinels of terra book.
Can I do an allied detachment from the sentinels book with Pedro Cantor as my HQ, a tactical squad, a sternguard squad then Assault Centurions from Fast Attack (plus dedicated transport) and something from heavy support?

[Learn2Eel]

Yep, all good to go! Though it doesn't really make sense, as far as I am aware, yes, Pedro can lead a Sentinels of Terra detachment.

[Shotgun Justice]

Cheers.
My thought process was: I'm building a death watch (sternguard) squad. I've got a limited edition marine captain with powerfist and bolter who I was going to use as a 9th company captain for my Ultramarines but he'd make a lovely deathwatch captain (Cantor). Cantor gives +1 attack, I dont own any centurions yet and they'd look cool as deathwatch, they dont have enough attacks so would fit him and his warlord trait. I can give them a dedicated land raider, in black. Cool.
it's either them or honour guard without the banner, to be counts as Deathwatch Vanguard equivalents but with bolters.