Your innate magic comes from sheer force of will alone.  Stubborn.  Unyielding.  Undeterred.  Your single-mindedness is so intense that it warps the Weave itself.  Your beliefs about reality, your own capabilities, and how the world should be are so pure and so powerful that reality bends to accommodate those beliefs.

Note: Due to the way DnD Beyond handles licensed content linked to homebrew (they don't allow linking, rather than just hiding it for users without specific licenses...) I've had to add all class spell lists to the "Additional Spell List" section of this subclass...  I am very sorry, this will force you to use filters while browsing for new spells.  This subclass can learn all Sorcerer spells, as well as any spells marked with Concentration from any class spell list.  Honor System!

Manifest Insubordination

You have a natural propensity for exerting your will on reality. Whenever you are forced to make a Concentration check, you may use your Reaction to gain Advantage to the check.

Additionally, whenever you would gain a new spell, you may select a spell of appropriate level from any class spell list, so long as it requires Concentration. That spell counts as a Sorcerer spell for you, and uses Charisma as its casting attribute.

Sheer Force of Will

By determined effort alone, you are able to maintain up to two spells requiring Concentration simultaneously.  Whenever you are required to make a Concentration check, you must make a separate check for each spell you are simultaneously maintaining.

Alternatively, so long as you are only maintaining a single Concentration spell, you may maintain that spell for up to twice its normal duration.

Starting at level 3, whenever you cast a spell requiring Concentration, you may spend 1 sorcery point. If you do, this spell no longer counts against your limit for simultaneously maintained Concentration spells.  You may only spend sorcery points in this manor to exempt up to a number of spells equal to your Charisma modifier at a time.  Your normal two Concentration spells maintained without sorcery points do not count toward this total.

Mind Over Matter

You will your body and mind to conform to your wishes, and they obey.  You MUST dodge that fireball.  You WILL NOT succumb to that poison.  Whenever you are forced to make a Saving Throw, you may spend 1 sorcery point to gain Advantage to the save.

Alternatively, you may spend 4 sorcery points to automatically succeed.

Refuse Reality

Starting at 14th level, when you take damage, or when you become subject to a spell effect, you can use your reaction to simply reject the indignity, and refuse to accept that this could possibly have happened to you.  If damaged, that damage is reduced by an amount equal to your sorcerer level.  If an effect, you may make a Charisma saving throw against the caster's DC.  You have Advantage on this save.

Impossible Resolve

Through unmitigated mental effort, you are able to assert impossible control over reality. You are now capable of maintaining a spell requiring Concentration indefinitely. You may only affect a single spell at a time with this ability. Attempting to maintain more than one Concentration spell beyond its duration simultaneously will immediately end all Concentration spells whose durations have elapsed.

Your dominating agency on existence now extends to all your magic.  Any non-Concentration spell you cast with a duration may instead be cast as a Concentration spell, with twice the duration.  All your abilities relating to Concentration spells can now affect that casting.