I came up with a variant 6th level feature for the Wild Magic Barbarian that I would like some feedback on. The idea is that during a rage the barbarian can focus its Wild Surge into a single casting of a low-level Sorcerer spell. This way, if the tide of battle turns so that your Wild Surge option is no longer useful (or it wasnt useful in the first place), you can instead use that magical energy to cast a spell whose effect you know. The tradeoffs are that 1) the spell cannot require concentration and 2) you can only cast the spell once and lose the benefit of your Wild Surge after that. Let me know what you think

Concentrated Arcana

6th-level Wild Magic feature, which replaces the Bolstering Magic feature

You learn one spell of 1st or 2nd level from the Sorcerer spell list, which cannot require concentration. While raging, you can focus the arcane power from your Wild Surge to cast the chosen spell. Constitution is your spellcasting modifier for this spell, and it is treated as being cast at a level equal to the value shown in the Rage Damage column of the Barbarian table. When casting the spell this way you do not need to provide material components which lack a cost, and you can perform the somatic component of the spell while holding a weapon or shield in one or both hands. 

After casting the spell this way, you lose the effect of your Wild Surge, and you cannot cast the spell this way again for the remainder of the rage . The effect of the spell ends early when your rage ends. 

Each time you finish a long rest, you can replace the spell learned through this feature with another spell from the Sorcerer spell list which follows the above criteria. Starting at 9th level the spell chosen can be up to 3rd level, and starting at 16th level the spell chosen can be up to 4th level. 

Seems a little too complicated to me... it feels like it would be one of those things that's more of a headache to keep up with than it's worth. It also makes the higher level Wild Magic Barbarian abilities virtually useless, since they're based on being able to more carefully curate your surge ability (either by re-rolling through taking damage, or by giving you advantage on your roll). If you choose to turn your Surge ability off to cast a single spell, then those future abilities go to waste.

That said, I do think that the Wild Magic Barbarian's 6th level ability is fairly lackluster, and the fact that it relies on a D3 of all things just makes it awkward. I do kind of like the idea of having some kind of "burst" effect that happens when your Rage ends... like if the enemy finds a way to purposely break your rage... either by not attacking or forcing your character to remain still in some way, then you get a quick reaction to retaliate. It might even make sense to deliberately stop your rage yourself... before you get the option to re-roll your Surge, you might find yourself with a Surge power that's either useless against a particular opponent, or actively gets in the way of other party members, and with this additional bonus when ending your Rage you might feel safe willingly ending your rage at the end of a turn for the chance to reroll in the future.

I feel like my idea is still pretty half-baked. I'm picturing it as basically being an AOE of Force damage that gets triggered, although maybe it would be good to have the option for it to be a burst of Temp HP for yourself and your allies instead. Just to make it a little more tactical.