I've always considered concentration was the worst enemy of a spell caster, as there are so many potent spells. However, I know that concentration is limited to limit the potency of these spells from playing off each other (such as spike growth and insect plague). However, I have designed a homebrew rule to allow more flexible casting, and I'd like some feedback on how good, bad, powerful, or weak it is.

-A spellcaster can concentrate on up to two spells at the same time. However, when a spellcaster does begin to concentrate on two spells, at the beginning of their turn every turn, they must make a concentration saving throw with a DC equal to 10 + the level of both spells combined. If the spellcaster fails this saving throw, they may select which of the two spells they lose concentration on.
-If a spellcaster concentrating on two spells at once takes damage, the DC is either 10 + the level of both spells combined or 1/2 the damage taken, whichever is higher. If the spellcaster fails this saving throw, they lose concentration on both spells.

Some things I have considered:
-War caster is basically a must for this to really be effective
-I was considering making the DC for taking damage harder
-I was considering giving the choice for the spellcaster if it fails the damage related saving throw under certain conditions (taking less damage, or so on)
-This could theoretically apply to more than 2 spells at the same time but I limited it to 2 as of now because my players are crazy and insane and will play all wizards just to concentrate on a million things at once and somehow have a +50,334,452,100 to concentration checks

What think, yay, nay, or may(be)

This looks similar to the Dual-focused feat from the original Tal`Dorei Campaign Settings:

Prerequisite: The ability to cast at least one spell

 

Countless hours have been spent training your mind to maintain focus on concurrent incantations, taxing as the process may be.

• If you attempt to cast a spell that requires concentration while already concentrating on an existing spell, you can maintain concentration on both spells simultaneously. You must spend a standard action each subsequent round on maintaining this concentration, or lose concentration for both spells.
• At the end of each turn where you have two spells you are concentrating on, you must make a Constitution saving throw (DC equals 10 + the number of complete rounds you've been concentrating on two spells). On a failure, you lose concentration for both spells. You can drop concentration on one of your spells during your turn as a free action to avoid this saving throw.
• Any time you would be forced to make a Constitution saving throw to maintain concentration due to taking damage, the DC equals 10 + both spells' levels combined, or half the damage you take, whichever number is higher. On a failure, you lose concentration on both spells.

-Tal'Dorei Campaign Settings p.108

It might mean something that this feat was dropped when they released Tal`Dorei Campaign Settings Reborn.

Quote from Mairondil >>

This looks similar to the Dual-focused feat from the original Tal`Dorei Campaign Settings:

Prerequisite: The ability to cast at least one spell

 

Countless hours have been spent training your mind to maintain focus on concurrent incantations, taxing as the process may be.

• If you attempt to cast a spell that requires concentration while already concentrating on an existing spell, you can maintain concentration on both spells simultaneously. You must spend a standard action each subsequent round on maintaining this concentration, or lose concentration for both spells.
• At the end of each turn where you have two spells you are concentrating on, you must make a Constitution saving throw (DC equals 10 + the number of complete rounds you've been concentrating on two spells). On a failure, you lose concentration for both spells. You can drop concentration on one of your spells during your turn as a free action to avoid this saving throw.
• Any time you would be forced to make a Constitution saving throw to maintain concentration due to taking damage, the DC equals 10 + both spells' levels combined, or half the damage you take, whichever number is higher. On a failure, you lose concentration on both spells.

-Tal'Dorei Campaign Settings p.108

It might mean something that this feat was dropped when they released Tal`Dorei Campaign Settings Reborn.

 

While they got rid of the feat, Moon Domain clerics still have a limited ability to concentrate on two spells at once

Channel Divinity: Mind of Two Moons

Starting at 6th level, you can use your Channel Divinity to invoke the twofold arcana of Exandria’s moons. By expending one use of Channel Divinity, you can cast a second concentration spell while already concentrating on a first spell, as long as both spells are on your list of Moon Domain spells. If you need to make a Constitution saving throw to maintain your concentration on both spells, you make the save with disadvantage. On a failure, you lose concentration on both spells.

Oh damn thats actually pretty much what I was looking for perfectly I didnt know it already existed, thanks man

Quote from TheBootedOne >>

Oh damn thats actually pretty much what I was looking for perfectly I didnt know it already existed, thanks man

It's not on dndbeyond, at least a legal published version isn't. I'm counting at least 5 or 6 that are community published that I'm fairly positive that they are not the original publishers, so I'm not going to link them.

Nothing stopping you from making a private homebrew version though.

EDIT

Geeze. There is 18 community published homebrew feats feats that literally have the starting sentence "Countless hours have been spent training your mind to maintain focus on concurrent incantations, taxing as the process may be." If you're going to plagiarize, at least add some salt and pepper and change that flavor a bit.