Here is an infusion combo I've been working on. 

Homunculus servant with a Enhanced defence shield. 

The HS can carry 60 pounds (4*15) and a shield is in 6 pounds. 

HS has a AC of 13+ the shield (2+1) for 16.it has evasion and can take the dodge action on its own. I wish Dex bonus was added to the AC. 

You order the HS to basically body block for you. Thus leaving your hands free for casting, tooling or other actions. You can also order it to do it's range attack still if needed. 

Just a quick idea, I think it would work RAW, but I might be mistaken. 

In RAW this doesn't work quite as you intend as the Homunculus Servant doesn't have any item proficiencies, so it can't benefit from holding the shield, so they would only get their base AC of 13.

In terms of it blocking attacks against you anyway, you can do this with any creature (including party members, innocent bystanders etc. as they all count as obstructions for the cover rules. However the effectiveness of this will depend how generous your DM is with the cover rules and the size of the shield; even a big tower shield might not block you entirely, in which case an enemy can still choose to target you instead, albeit with you having a bonus for half or two-thirds cover, so it won't matter if the Homunculus is dodging. As for Evasion, unless the DM grants total cover you're getting hit anyway so this only benefits the Homunculus that is caught in the blast.

You'd definitely have to discuss with your DM, as my main groups are pretty lax when it comes to the cover rules (both DMs and players). One of my characters is Large (using my Brute Minotaur rules) and one big benefit of that is that she is basically mobile cover to the party, and is built to be a damage sponge as a result, but I do have to keep reminding players and the DM that she can be used as cover (I mean technically anyone can be, but she's big enough to block sight entirely with a little coordination so it can be more effective).

On which note, if your DM does allow it, keep in mind that the Homonculus Servant isn't very tough; while it has some decent defensive boosts it doesn't take much to take it out, especially if targeted by something other than an attack or DEX save.

It's a fun idea, and you should definitely discuss with your DM how far they're willing to let you take it, and what trade offs they might ask for. If it were me I would maybe let it count as you having the shield (so long as it's between you and the attacker), but covering you would be all the Homunculus could do in its turn, i.e- it couldn't still attack though it could use its reaction as normal? That's heavily homebrew territory though.

You don't have to be proficient with a shield to benefit from it, you just incur drawbacks while wearing it.

Armor Proficiency. Anyone can put on a suit of armor or strap a shield to an arm. Only those proficient in the armor’s use know how to wear it effectively, however. Your class gives you proficiency with certain types of armor. If you wear armor that you lack proficiency with, you have disadvantage on any ability check, saving throw, or attack roll that involves Strength or Dexterity, and you can’t cast spells.

And yeah I think have the homunculus block for you is DM fiat territory.

Whoops, right you are; I thought that was just for regular armour! While you'll get the AC in that case, that's quite a serious penalty for the Homunculus, as disadvantage on DEX saves is going to mean you don't get the benefit of Evasion as easily, and half damage will still pretty reliably wipe out a Homunculus.

I don't have anything to add to the conversation, but wanted to clarify that the Homunculus is size Tiny so it's carry weight is halved to 30 lbs.