Optimising 5.5 Artificer

How would you build the most powerful artificer in 5.5e? Which subclass would you choose? Which spells, feats, species, etc would you choose?

(Artificer is the class I am least familiar with so I'm just curious what everyone else does with it. I'm not looking for specific advice, this is just a thought experiment.)

Armorer subclass, gives you full plate and shield at level 3, ac is 20. You get mirror image spell, so the hits that get through ac have to then get through mirror image.

Infiltrator armor model gives you a lughtning launcher mounted on your armor chestplate, so you can fire it with both hands full. It uses intelligence for hit and damage. Another model has punching fists. And another has a wrecking ball. 

The way the build works, pick a model with melee, cast mirror image, and tank like theres no tomorrow.

Youre a half caater, so you get second level spells a bit later, but that will unlock a homunculus, basically a familiar that has a built in attack, and doesnt require your action for it to attack. It can fly, and has telepathy to 1 mile, but you cant see through it. Its basically a voice controlled drone, not an fpv drone. Once you get homunculus, it can kite around you and do a 30ft ranged attack that does force damage.

At level 7 (i think) you get "Flash of Genius" which lets you use your reaction to add your INTMOD to a saving throw you or someone withing 30 ft of you failed. You can do this intmod times per long rest. Its like a watered down paladins aura. I have used it many, many times to save myself or a party member from very vad outcomes.

At level 10, your replicate magic item feature can make elemental gems every day, so you can have one earth elemental, one water elemental, one air elmental, one fire elemental each day. Once summoned, they last for 1 hour or until hp is 0.

At level 11, you get spell storing item, which lets you put one artificer spell up to level 3 into the item. Anyone can the use item to cast that spell 10 times per long rest. Biggest damaging spell for armorer is Lightning Bolt, which does 8d6 lightning damage.

At level 14, your replicate magic item feature can makr pretty much any rare magic item.

The replicate magic item feature basically lets you make magic items up to a certain rarity. This rarity increases at level 6,10, 14.  At level 14, yoh can make rare items. Normally, by level 14, you have already acquired or purchased all the magic items you want. So this feature seems best used for making single-use summoning items that dont require attunement. You get more attunement slots at higher level, but it wont be enough, so you will want to pick replicate magic item plans that dont require attunement. Elemental gems are a good start, once they unlock for you. They are single use items generally, but you can build new ones afte revery long rest.

At level 15, i think, one of the armor models can fly, basically making you Ironman.

And your Capstone feat is crazy good.

A great deal of an Artificer's power is from the investment in their INT score. Getting it to 18 and then 20 will be reflected in nearly every round of initiative.