Is this modification to the sharpshooter feat balanced?

Question

I'm DMing a 5e campaign, and one of the players is a ranger (currently level 1) who wants to be able to shoot two arrows at once. I said he could do so, but at disadvantage for both arrows, which I just homebrewed on the spot.

At level 4, when they get a feat, I'm thinking about adding an extra option to the sharpshooter feat: the player can choose to take of -5 to hit for +10 damage (as per normal) or they can choose to take -5 to hit, make one attack roll and hit two enemies that are within 5 feet of each other.

(To reiterate, this adds a fourth benefit to the feat; it doesn't replace the third. Both options would be available to the player with this modification. The player can choose either option but has access to both at all times.)

This may be a tad overpowered, but I'm thinking maybe add that you must have the Archery Fighting Style for this option and you must have at least 20 feet between you and the targets.

From a balance perspective, is this a reasonable addition? Does it require more restrictions?

Answer 1

The current edit on the question changes the answer significantly.

As mentioned by András, the Sharpshooter is already one of the strongest feats in the game. Adding versatility to it makes a feat that is already "must take" for ranged characters incredibly broken, imho.

You are making it too strong, because it is already strong.

I'll state it again to make it clear: the problem is not exactly your addition, but the fact that the feat is already strong as it is and any addition to it makes it too strong, from my point of view.

You need to add a trade-off

Instead of just making it stronger by adding another option, make it a trade-off. If you want to add another option, then you lose something on the other options. Also, you should make it in such a way that choosing between hitting only one or two targets is actually a choice.

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Disclaimer: I have not tried these homebrew-changes to the sharpshooter feat, so the following is theorycrafting. I'm putting these into answer as ideas to the person making the question and to give examples of what I mean by adding a trade-off. The question itself was already answered in the previous section - no, it's not reasonable to add something to the sharpshooter feat and yes it needs more restrictions.

The changes I would make are the both that follow: (Both, not choose one)

The second arrow doesn't add your damage

Similar to Dual Wielding for melee fighters, a possible and easy nerf is to make the second arrow do only the flat damage, instead of the damage plus dex bonus.

The third option of Sharpshooter gets nerfed a little

To +7 or +8 damage. Honestly, it would need playtest to get to an accurate value that makes the trade-off between hitting two targets instead of only one an actual decision instad of "hitting only one is always better" or "splitting is always better when possible".

Answer 2

It is significantly weaker than the original Sharpshooter

While the original Sharpshooter is one of the strongest feats in the game, this modification pushes it into the barely viable category.

Comparison

You propose to keep the penalty (-5), but reduce the benefit.
While with a Longbow and 20 Dex your average damage is 10.5, it must target another enemy. Spreading damage is usually less effective than bringing one enemy down quickly; two Ogres at half hit points do twice as much damage as one alive and one dead. There might not even be a secondary target in range.
For this reason damage to secondary targets were calculated halved on the now defunct WotC forums.

So the benefit is 5.25 with a Longbow, more if magical, less with different ranged weapons.

Proposal

Reduce the penalty to -3, it keeps the benefit / cost ratio around 2.

Answer 3

It is balanced

Adding another, significantly weaker option will not make Sharpshooter overpowered, as it will hardly be used.
The new option is only good if you know that the primary target has only a few hit points, and you are sure you will hit it. These are hard to konw, and in any other case the original Sharpshooter or an unmodified attack is much better.

So yes, Sharpshooter is strong, but this will not make it noticeably stronger.