"Arcane Emission Gauntlets" is pretty junky. What level 14 PC is going to expend an action on doing 10 damage, even in an AOE?

Two upgrades at level 6 might be a bit much (2 elixers, and 1d12, and ability to burn 1st level slots on the 9-12 abilities).

The charges, can't artificers just make brand new ones every long rest? Your complex recharge mechanics become "at the end of a long rest, the artificer gives it full charges", no? Ok, I guess there are annoying juggling rules to end infusions early; ie, you have to have 2 copies of the mundane item.

Still.

The wielder of the shield can apply the shield's AC bonus to savings throws and ability checks made to resist being forcibly moved.
How about "while not incapacitated, the wielder of the shield cannot be forcibly moved or knocked prone without their consent".

We are talking 14th level here.
While wearing this helmet, a creature has advantage on saving throws against being stunned, charmed, and frightened.
"and advantage on saving throws against effects a creature immune to being stunned, charmed and frightened would be immune to".

Just because.
While wielding the weapon with both hands, a creature gains a +1 bonus to AC. This bonus does not stack with the bonus to AC from a shield.

The bonus increases to +2 when you reach 10th level in this class.
Stack is not a 5e game term.

"While wielding this weapon and not wielding a shield, a creature gains a +1 bonus to AC".

I mean, as written, trading a 1d10 longsword damage for a 2d6 greatsword is worth about 1 AC; so you have an item where you are burning an attunement slot to get an even trade.
Empowered Spell Ring
Annoyingly this works better on a non-artificer than an artificer.

How about:

"When casting a spell that deals that damage using a spell slot, you can expend a charge to treat it as being cast with a spell slot level equal to your proficiency bonus."

So you cast a 1st level acid spell, and with this it is cast as if you used a 6th level slot. Or a 3rd level fireball; also 6th level slot (at level 17+).

Still useful to all casters, but more useful to an artificer, who has lower level slots.

Experimental Elixir
As noted, one of the big problems is the slot cost of artificer levels.

What if we gave them more Elixers? Like, starting at 6th level, you make half your artificer level in elixers. Drinks for everyone!

Then make it 1d6 at level 3, 1d8 at level 5, 1d10 at level 11 and 1d12 at level 17, to align with the tier steps.

...you choose the elixirís effect from any Experimental Elixir effect you could make.
when you use a spell slot.

Then take a run at the elixers, and make scale more smoothly at each tier.

Healing: 2d4+Intelligence modifier healing. At 5th level you can drink this Elixer as a bonus action. At 11th and 17th level add another 2d4 to the amount healed.
Swiftness: 10' increased walking speed for 1 hour, increasing by 5' at level 5, 11 and 17. At 11th level you can also dash as a bonus action, and at 17th level you can take a bonus action to both dash and disengage.
Resilience: The drinker gets a +1 bonus to AC, increasing to +2 at level 5. At level 11 no creature can gain advantage on attacks on them, and at level 17 they gain resistance to non-magical bludgeoning, piercing and slashing damage.
Boldness: The drinker can roll a d4 and add the number rolled to every attack roll and saving throw they make for the next minute. At 5th level you can drink this potion as a bonus action. At 11th level, you can end this effect to gain a +5 bonus to an attack roll or saving throw after you have seen the roll, in addition to this potions +1d4. At 17th level, you instead gain a +1d6 bonus to attack rolls and saving throws.
Flight: The drinker gains a flying speed of 10 feet for 10 minutes with a height limit of 50'. At 5th, 11th and 17th level the flying speed increases by 10 feet and the height limit increases by 50'.
Transformation: The drinkerís body is transformed as if by the alter self spell. The drinker determines the transformation caused by the spell, the effects of which last for 1 minute or until they end the effect as an action. At 5th level the duration increases to 10 minutes, at 11th to 24 hours, and to 17th level it lasts until dispelled.
Third Eye: The drinker gains blindsight with a 20' range. This range increases by 20' at level 5, 11 and 17. In addition, at 11th level they can see Invisible and Ethereal creatures within this radius, and at 17th level they have Truesight within that radius.
Darksight: The drinker gains darkvision with a range of 60 feet for 1 hour if they do not already posses it, or an additional 20' if they already do. At 5th and 11th level the range of their darkvision increases by 20'. At 11th level, magical darkness doesn't impede the drinker's darkvision, and at 17th level the range of their darkvision is unlimited.
Emission: The drinker gains the effects of the dragon's breath spell for 1 minute (choose the damage type when you create the elixir). At 5th level they can drink this potion as a bonus action, at 11th level the drinker can exhale the dragon's breath as part of the action used to drink the elixer, and at 17th level the drinker can exhale the dragon's breath as a bonus action instead of an action.
Hexed Form: The drinkerís body is transformed as if by the polymorph spell. The drinker determines the transformation caused by the spell, which must be into a CR 0 beast. The effects last for 10 minutes or until the drinker ends it as an action. At 5th level the duration increases to 1 hour, at 11th level beasts up to CR 1 can be transformed into, and at 17th level the effect lasts until dispelled.
Suave: The drinker can roll a d4 and add the number rolled to every ability check they make for the next 1 minute. At 5th level the duration increases to 10 minutes, at 11th level the drinker can end the effect to gain an additional +5 bonus to an ability check, and at 17th level the bonus becomes 1d6 instead of 1d4.
Antitoxin: The drinker becomes immune to poison damage and the poisoned condition for 1 minute. At 5th level the duration increases to 10 minutes, at 11th level the drinker becomes immune to all disease and has advantage on all constitution saving throws except concentration saving throws, and at 17th level the duration becomes 24 hours.

The idea is that the low level effects remain awesome, because they scale with artificer level.