How about a completely different way to cast spells as a Sorcerer in 5e?
Magic is in your blood….., and in blood in general. Life is power, and you know how to extract power from your own life.
Power in the blood
You no longer have a Sorcery Points pool, but you add any point you would gain as hit points. You also no longer have a limit to the number of spells you can cast per day. When you cast a spell of any level, lose double the spell level in hit points. You can cast spells as long you still have positive, non-zero hit points, but you must take the damage. Cantrips cause one hit-point loss.
Spilled blood, released power
Starting at 6th level, when you are dealt damage as a reaction you can use that hit point loss to cast one spell as a reaction. The spell level must be less then or equal to double the lost hit point total. You do not take damage for casting this spell. You can not use this ability again until you take a short or long rest.
Starting at 14th, another can donate a small vial of blood to you. Another creature can take any amount of damage and donate that damage to you as hit points you can use to cast spells. A creature can take up to 30 point of damage. You can use these points of damage as you would normally use hit point for Power in the Blood. This donation of blood is usable until that creature takes a long rest.
Starting at 18 level, you can now use the suffering of your targets to energize your spells. As a swift action on your turn, when you cause damage to a creature using one of your spells, you can capture up to double your level in hit points of damage from that creature. You can use these points of damage as you would normally use hit point for Power in the Blood. You must use these points within an hour. Or, the power leaves them, and they are lost. You can not use this power until you take another long rest.