Basically I'm wondering if I should do a pure armorer build or go for a slight warlock dip? It would just be 2 levels for Eldritch blast and agonizing blast invocation for a solid long range cantrip, but then I'm missing out on the level 20 ability (assuming we ever get that far). It's really just a flavor decision as I'm building an "Iron Man" type character and I think this plus guardian is better than the lightning launcher option.

Plus warlock (hex blade) gets me the shield spell which artificer doesn't actually get...

I'm also considering 5 artificer/2 warlock/and the rest in sorcerer for more spells, but that's another topic.

Anyway thoughts?

Warlock doesn't synergize well with artificer.  If you're looking to get a ranged cantrip option and Shield, you're better off picking up a level of wizard or grabbing the Magic Initiate (Wizard) feat.

It sounds like you're playing with 5e but assuming that you are playing with the 2024 rules, are playing as the yet to release Artificer from Forge of the Artificer (or the last relevant Unearthed Arcana) and can use older content as well, I think multiclassing Artificer Armorer with Warlock can work, with just the minimum requirement of 13 Charisma to multiclass but it would be a while for it to pay off. As 6thLyranGuard said, you can grab the Magic Initiate (Wizard) Origin Feat at Level 1, and choose Shield as the associated Level 1 Wizard Spell. Go Artificer for Levels 2 and 3 to get Armorer.

At level 4 switch to Warlock. Yes, you can grab Eldritch Blast at this point but later you can cast it using Intelligence instead. Maybe choose Eldritch Mind for your Invocation or Pact of the Chain. At level 5, pick any Invocation you think would be good for your party EXCEPT FOR AGONIZING BLAST.

Because at Level 6, you switch back to Artificer (Artificer 4, Warlock 2) and from Tasha's Cauldron of Everything, you can grab the Feat Eldritch Adept, which you can choose Intelligence as the associated spellcasting ability. You now qualify to take Agonizing Blast as the Invocation. With this you can at least add your intelligence modifier.

Staying with Artificer until Level 12 (Artificer 10, Warlock 2), you can now pick Uncommon Wonderous Items as one of your Magic Items. Here I say that you grab, from Tasha's Cauldron of Everything, the All-Purpose Tool+1. "As an action, you can focus on the tool to channel your creative forces. Choose a cantrip that you don't know from any class list. For 8 hours, you can cast that cantrip, and it counts as an artificer cantrip for you." You can choose Eldritch Blast with this feature. You can now cast Eldritch Blast using your Intelligence Modifier, plus 1 to hit from the All-Purpose Tool, and add your Intelligence Modifier to damage thanks to Eldritch Adept.

That's Eldritch Blast, Agonizing Blast, and Shield. I know going that far into Artificer may not be that exciting spell-wise, but you do get to effectively pick your own magic items to a certain extent (like Mind Sharpener, maybe, so you would definitely never drop concentration on a spell.) If your table is one where your party doesn't get that many items, this may work in your favor better than if your DM has plenty of goodies waiting for you.

Also, I know you were considering Sorcerer for more spells, but may I interest you in at least 3 levels into Wizard after all that is said and done to grab the Evoker subclass and their Potent Cantrip feature? "Your damaging cantrips affect even creatures that avoid the brunt of the effect. When you cast a cantrip at a creature and you miss with the attack roll or the target succeeds on a saving throw against the cantrip, the target takes half the cantrip’s damage (if any)..." At this point you would be level 15 (Artificer 10, Warlock 2, Wizard 3), so you would have 3 beams for your Eldritch Blast. That's 3 attacks that will definitely do some damage.

Anyways, am excited to hear what you end up playing no matter what you choose and good luck out there!

I'd also like to point out that most campaigns end before the party reaches 10th level, so any multiclass build that takes longer than that to mature is probably not going to happen.

I would stay pure Armorer, and use the lightning launcher instead of Eldritch Blast.

What you are giving up just to gain the Shield spell and Eldritch Blast isn't worth it, and has been pointed out, Shield can be gained other ways if you truly have your heart set on it. If you are looking for a 1 level dip, go Rogue or Wizard. Wizard would give you that Shield spell (and Wizard uses the same stat that your Artificer likely already has), Rogue would add a d6 sneak to your lightning launcher's 2d6 damage.

The lightning launcher actually has a longer range than Eldritch Blast (without feats to extend the range) and a higher average damage per hit, and by not multi-classing you stand a better chance of getting the higher abilities of the Armorer class. Also, unless each of your multi-classed levels are evenly divisible by 4, multi-classing puts you behind the curve on the gaining of Feats/Ability Score Adjustments. A 1 level dip isn't too bad, 2 is pushing it, but 3 is a real disadvantage to be avoided.

So my advice, pure Armorer Artificer, but if you really really want to multi-class, go 1 level of either Rogue or Wizard with all other levels in Artificer. If you are playing an Artificer you likely already have an INT and DEX at or above 13, you might not have a CHA at or above 13 (and your to hit bonus with that Eldritch Blast will use Cha not your highest score).