I have a minor homebrew tweak that I am using, just looking to get opinions from you fine folks.

I think the biggest appeal to the Artificer is the idea of making magic items! Finding items within the depths of a dungeon is fun, but what I really want is to create my own custom gear. There's no 'in class' measure for making items, you just make them like anyone else would. Which seems lame for a character designed to craft items. So I thought it would make sense if anytime a character learned a new infusion they'd gain one permanent version of the item.

Think of it this way
Your character has spent weeks, months, maybe years trying to learn how to make x item[substitute x for bag of holding]. They've put in the hours crafting the perfect bag. Made of the finest leather and constructed with beautifully detailed stitching. They now have their very own bag of holding. After all this time they know how bags of holding are made and can now also make temporary replicas with relative ease [infusions].
To make a second permanent bag of holding would take all of the hours and coin as it would usually take because 'permanent' magic takes more time and care than infusions which are by their nature temporary magic that can be easily dismissed or recreated.

Enormously vulnerable to exploitation.  Also not even the slightest bit minor.

First of all, this means the character gains twelve free magic items throughout their career minimum, which can be bought, sold, traded, or whatever'd without a care because they're permanent.  5e assumes a character is lucky if it has a full set of three items by 20th level.  

Second of all, artificers are allowed to change one of their infusions for a new one on level-up.  Under your rule as written, they'd gain a new free magic item whenever they did so.  I get that you clearly wouldn't allow this, but someone reading your rule in a book would say "wow!  I can just keep changing them out to get a ton of loot!" and bamboozle the system.

If you wanted to do something like this, and were okay with your artificer being well above the curve in permanent items, I would change it to something like this:
"At 2nd, 6th, 10th, 14th, and 18th levels, your artificer learns new Magic Infusions that allows them to mimic the effects of powerful magical items.  At each of these levels, the artificer's research and experimentation pays off, allowing them to create one item in their spare time with materials scrounged through adventuring.  At each of the mentioned levels, choose one of the new infusions your artificer is learning.  They gain one copy of that item as part of gaining new Infusions."

I actually totally forgot about being able to change out infusions. You're right, I'd absolutely not count that as gaining a new permanent item. [I actually don't even like the idea of 'forgetting' infusions you know for new ones. It's a weird mechanic, but not exactly going to get in the way of me playing.]

I did actually think of going for one permanent item instead of two, but I suppose my group tends to have more magic items in general because 3 seems absolutely pitiful for a level 20 character. Plus since I view artificer as support [though it doesn't have to be given versatility] the aim of permanent items is to give them to other players. Given how big my group is, that many items isn't much.

This is all situational however. I can defiantly see how it could be abused, and I by no means think this should be a legitimate change to the artificer. Just an idea I had that works for me, and might for others as well.

I like the idea that when an Artificer infuses an item they learn how to make a more permanent version of that magic item but still need to spend the appropriate time and resources to do so, the infused item itself is a temporary prototype designed to serve until the more permanent version is complete then the artificer can swap out the known infusion (retaining the knowledge of how to craft the item) for a new one next level to experiment with and eventually replace.

My notion is that anything the artificer has the Infusion for qualifies for the "half the cost, quarter of the time" discount from Magic item Adept, so long as you have that infusion the entire time you're crafting the item.  If the infusion is supposed to serve as a prototype, there's no reason the artificer can't use it as a springboard to make the final crafting easier.  It does technically allow semi-early access to a 10th-level class feature, but the artificer class as a whole is on the weaker side and people mostly make artificers to do ONE THING, so in this case I figure it's allowable.

Quote from Yurei1453 >>

My notion is that anything the artificer has the Infusion for qualifies for the "half the cost, quarter of the time" discount from Magic item Adept, so long as you have that infusion the entire time you're crafting the item.  If the infusion is supposed to serve as a prototype, there's no reason the artificer can't use it as a springboard to make the final crafting easier.  It does technically allow semi-early access to a 10th-level class feature, but the artificer class as a whole is on the weaker side and people mostly make artificers to do ONE THING, so in this case I figure it's allowable.

 Ah,,, Okay I totally understand this. I think maybe our perceptions of leveling up are a bit different? Which is why I got it backwards from you. If I had a DM that wanted me to play this way I'd totally be fine with it, but I look at it this way-

Realistically not all characters get stronger from battle alone. It depends on class[es]. An artificer would level up via intensive study/research/crafting. They'd have to spend all that time and money to craft the magic items, and then once they finally reach the goal in theory that's their leveling up point.
I'm preferential to milestone levels instead of XP levels, which I don't think would translate well into this idea at all.