a few things: This is a really low model count for a 30k army, and while that kind of army could work, the UM special really count on you having a lot of units on the board. Secondly, this list isn't as durable as you may think. 30 power armour marines will drop like flies, even with a rhino or dreadclaw backing them up. Additionally, if you use this as you're army, you also partially lock yourself out of both Rights of War, Support officer Centurions, and so long as the dreadclaw is there, you can't take the UM specific RoW. Maybe look at something along these lines:
1 praetor w/ whatever right of war (using the UM one for this example)
1 Master of Signal
2 20-man tactical squads
10-man support squad
3 quad mortars w/ shatter
Deredeo
10-man seige tyrant rip-offs
from there, I would continue to add units to make the most of the UM legion buffs. Maybe guilliman and some of the invictus?