Headscratcher: Where Are My Iron Warriors Headed?

 G'day folks, Macca here with some pondering and some questions for those who may be reading. For some time now, I have been working on my Iron Warriors project, and it is coming along pretty nicely. However, I have hit some snags.

The Background:

The force is based off the descriptions in Book III: Extermination about the battle of Paramar. Basically, a small Iron Warrior force, a segment of the 77th Grand Battalion, is ambushed by the Alpha Legion who are trying to conquer Paramar. The 77th having been isolated from their Legion for some time, are furious at the betrayal and commit their forces en masse to bolster Paramar against the Hydra.

As they were only a few ships and a small compliment of warriors, the Iron Warriors did what they do best: dug in and fortified the hell out of the planet, even as the vastly superior Alpha Legion moved in. During the land phase, the Iron Warriors emerged from concealed positions and engaged the Alpha Legion armour at point blank with dreadnought rush and with all the armour they had available. In the end however, the Alpha Legion won the battle, but Kyr Vhalen survived, dragged spitting blood and curses from his shattered command bunker.

Cool.

HQ:

At the time of writing this, I have Kyr Vhalen, a Siege Breaker (or Praetor), a Master of Signals (magnetised to also act as a Primus Medicae) and as of last night a Librarian. These are of course backed by a formidable command squad.

The commanders are probably the best organised segment of the army, because I find building and kitbashing HQ's to be immensely rewarding.

Elites:

With the elites, I am very well endowed, with a full squad of Tyrant Terminators, a small squad of Destroyers, and a pair of Contemptors. There is room however to expand here, as I doubt I will use the Destroyers much, and I would rather focus on my Dreadnoughts and Terminators here.

I would like to either:

-get more Dreadnoughts
-get some Rapiers
-both?

Troops:

The troops area is the most bland area. At the moment, it's just a couple of tactical squads. I will eventually add a third tac squad, and maybe a tac support squad or breachers, but for now, I am using them to provide numbers of line troops.

Fast Attack:

What is this slot?

Heavy Support:

I am pretty full on with ideas here, and it's where the real snags occur. I have two Iron Havok squads at the moment, one with shrapnel heavy bolters, and one with autocannons. The shrapnel heavy bolters suck, but the autocannons are amazing. The whole thought process here is that when Kyr deployed his troops, every heavy weapon he had was put on the line. I like the idea of these units, not their function in-game.

The problem is however, I now have TWO slots still to fill. What do I take? I don't want Artillery. It's Iron Warrior-y, but it isn't Paramar, they weren't pulling a Krieg here, they were sending all the grunts into the trenches and rushing the Alpha Legion with massed armour. I'm thinking:

-Vindicator, maybe two?
-Deredeo Dreadnought, maybe two, one with plasma, the other with regular dakka.
-Predator squad with plasma? I can't remember if I can take that or not in 30k...

My thinking here being that the army desperately needs AP2 options, as every ranged option so far is ap3 or worse. If the other guy has artificer armour, or terminators, I'm in the ouch zone.

Lord of War:

So far, I have just one: The Tormentor. It's cool and all, but not present in the battle, as Perturabo was busy team killing on Istvaan V. I'm thinking a Typhon would be the best fit here theme wise and game wise.

So, can anybody give me ideas? My poor Iron Warriors are in desperate need or more dakka!