I have wanted a Power Armor / Munitions mix toon for some time but there are some difficulties in getting these 2 sets to play nicely together. After answering another posters question about how to combine these sets, I actually got off my lazy butt and researched what would work best. This is the build I'm currently using for my Tyrant Vomit character. I retconned at 17, when I started doing the research.
Level 29 build (not 40 yet)
Superstats:
Level 6: Super Dexterity
Level 13: Super Recovery
Powers:
Level 1: Gun Slinger
Level 1: Shotgun -- Breaching Round, Rank 2, Accelerated Metabolism
Level 5: Killer Instinct
Level 5: Jet Boots -- Rank 2
Level 8: Force Shield -- Force Sheath
Level 11: Gatling Gun -- Accelerated Metabolism, Rank 2, Rank 3
Level 14: Invulnerability -- Rank 2, Rank 3
Level 17: Breakaway Shot (I wish I had taken Evasive Maneuvers instead for the lower cost)
Level 20: Lock/Load
Level 23: Unbreakable -- Better You Than Me
Level 26: Shoulder Launcher -- Rank 2
Level 29: Bionic Shielding -- Overloaded Circuits

Talents:
Level 1: Absolute Zero
Level 6: Agile
Level 9: Tireless
Level 12: Shooter
Level 15: Worldly
Level 18 Martial Training
Level 21: Impresario
Force Shield with Force Sheath is so important. It provides continuing protection and energy gain for a few seconds after blocking. And it looks like a cool high-tech energy shield. I usually turn it on before attacking mobs.
I went with the maximum damage for Gatling Gun instead of adding the Fear Advantage, but that Advantage can be very useful too.
With the Invulnerability Passive, Unbreakable Active Defense, and Bionic Shielding this build is very survivable so the main concern is having enough juice to spray Death all over your opponents. My next Power will probably be Form of the Tempest because it adds a little energy with each Critical Hit. My next Power after that might be some kind of melee attack because of FoT gives Focus and Breakaway Shot is so darn expensive.

I should say here that I only do PvE. I cannot make any claims about how this build would work in PvP.

The Shoulder Launcher is the only Power Armor set weapon on this build. I think it's better than the Rocket Launcher and plus my Battle Suit concept required a mounted missile launcher. It's a Tier 3 PA set Power, so I had to wait until lvl 26 to get it. But, It's worth the wait.
I just added the Bionic Shielding w/ Overloaded Circuits. I have only tested it in the Power House Test Room so far but the idea that it will send electric damage to people who attack me is another cool high-tech looking idea.
With most Henchmen mobs that I hit with Shoulder Launcher the main target dies and the rest are wounded and easy to clean up with the Gat. I haven't 1-shot any Villains yet. I hit them with the SL, recharge Force Sheath while they run into 50 feet range, I Shotgun them a couple times which knocks them back and finish with Gat.
When facing a big boss, I make sure I charge Force Shield, hit Lock and Load, and wale on the Boss for a while. You have to take time to block or risk running out of energy.
So while this is mainly a Munitions build, it looks cool, kicks butt, and doesn't die easily.

If I could afford to, I would replace Breakaway Shot with Evasive Maneuvers. I would have gotten Bionic Shielding instead of Unbreakable. That Unbreakable Advantage, Better You than Me, will be useless once I get Form of the Tempest. I might just go and retcon that.

My next step is to research ways to be more energy efficient. Anyone have some hints?
My Rec is pretty much at it's max for benefits, so I might add a little End from gear. I've been considering making an Arms item that would reduce my power costs but haven't experimented with that yet. My current stats give me 27% Crit chance with 56% severity. My Primary Defense is my only Con gear. I do use an item that grants energy upon enemy defeat. I can usually go through 2 groups of mobs before running out of energy. Is that pretty good? Problem is maintaining energy during Boss fights.

I know very little about combinding power sets or even how to get the most out of a single set.
But isnt the main appeal to PA the ability to fire 3 weapon systems at once?, normaly Conc beams, minigun and micro munitions.

I notice you only have shoulder launcher. While I like this power, it is a pain to use do to the energy cost is taken upfront and if your knocked back,pushed back, stun or even turn the attack is cancled. and this happens far more than you might think.

I'm not sure you can really call with a munitions/PA mix if you only have 1 PA attack power.

thats my 2cents, if its even worth that much.

No problem. I appreciate the feedback, that's why I posted on the Forum.
I have actually used Shoulder Launcher while beings mobbed by some mobs. Maybe they all missed or something. I have Rec as a SS, so I have the energy to use SL from stop.
I guess you're right, I can't really call it a Mun/PA mix if I'm just mainly using passives and buffs from PA. So, it's basically a Munitions build.

if you lose Unbreakable with the advantage that only leaves you with Gatling gun for enrage, so ya might drop as well drop breaching round on shotty too

I've found that the Min Gun is much better as a shoulder slot. Because of the damage resist debuff, it ends up allowing you to do much more damage in the long run.

I'm working on something similar based on Boba Fett, and I'm probably going to go CON/REC with Defiance as a passive. With Force Shield/Force Sheath, that should take care of my energy issues, and let me use Imbue to autocrit effectively with my opening attack. We'll see how well it works.

That Mini Gun debuff is awesome. But it won't give me energy from Killer Instinct. My concept required a big freaking gun anyways.
During this Blood Moon, I was able to get around 3 full maintains of the Gat (refreshing Force Sheath between) because of my Energy on Kill Item. I would target the Boss and make sure my fire would hit zombies too. I bet Mini Gun could do that too.