Active Concentration

[Yunru]

Not sure if this would be a feat, class ability, or just a base thing anyone could do:

"When you cast a spell with a casting time of one action or less that requires concentration, you may forgo concentrating on that spell. If you do, on each following turn you may spend the same action as the spell's casting time to maintain it. The spell lasts for the full duration unless you choose not to maintain it."

First of all, the wording feels a bit clunky, so any help cleaning it up is appreciated.
Secondly, the impact. This would allow two concentration spells at once (or one without any checks if in a high damage environment), but would also eat up your capabilities beyond just the first casting. Obviously it's also not compatible with spells like Call Lightning which allow you to do stuff with your action due to the action economy.

[DeTess]

Not sure if this would be a feat, class ability, or just a base thing anyone could do:

"When you cast a spell with a casting time of one action or less that requires concentration, you may forgo concentrating on that spell. If you do, on each following turn you may spend the same action as the spell's casting time to maintain it. The spell lasts for the full duration unless you choose not to maintain it."

First of all, the wording feels a bit clunky, so any help cleaning it up is appreciated.
Secondly, the impact. This would allow two concentration spells at once (or one without any checks if in a high damage environment), but would also eat up your capabilities beyond just the first casting. Obviously it's also not compatible with spells like Call Lightning which allow you to do stuff with your action due to the action economy.

The wording looks fairly clear. I'm just not certain if this is something you want to do. There are out-of-combat cases where this is nice (for example, keeping up both fly and invisibility for the party), but in-combat this'll either be sub-optimal, and therefore won't be used, or it is optimal, and lead to a boring play-style. A more interesting way to approach it might be to have it set your movement speed to 0 and/or reduce your defenses (for example, you lose your dex bonus to AC or everyone has advantage to hit you). That way you can still influence the fight actively, but you're at greater risk so its a more situational boon.