SSJ: Sun Soul Jmonk(?)

This subclass aim to boost the damage dealer identity of the monk, and also giving some tools to work around the main weanesses of the class, such as being comically squishy and have and hard time against swarms of enemies.

Sun Warrior

Solar Fists: Starting at level 3 you can choose to inflict radiant damage with your unarmed strikes. Your unarmed strikes have a range of 9 meters, if you use them as a ranged attack the damage type will be radiant.

Spotted Skin: You've been grilling without a shirt and sunscreen long enough, some very healthy spots appear on your skin. Starting at level 3 you are resistant to radiant damage.

Level 3: Celestial acolyte

Solar Imitation: Starting at level 3 you gain the Light cantrip. Starting at level 11, the light produced by this cantrip is considered sunlight.

Celestial Compass: Starting from level 3 you always know which direction the sun is facing.

Level 6: Solar muscles

Starting at level 6 you can spend 2 ki points to create a manifestation of your life force. This materializes around your body as a red flame that produces no heat and generates dim light for 1 and a half meters around you until the end of the turn. All your unarmed strikes deal an additional 1d4 fire damage until the end of the turn. Damage increases to 1d6 at level 11, and 1d8 at level 17.

Level 6: Sunstrike

Starting at level 6 you can generate a 15-foot, square-based cone of light as a magical action. To cast this spell you must be able to fold your hands in front of you, forming a triangle with them. All creatures illuminated by this light must succeed on a Constitution saving throw or be blinded until the end of your next turn. The first time you use this benefit you do not need to spend ki points, starting from the second time you will have to use 2 ki points. Use resumes at sunrise.

Level 11: Solar barrage

At level 11 you gain the solar barrage spell. This spell requires an action to cast and lasts instantaneously. You can cast this spell without using spell slots, but you can only do so once, usage resets at dawn. This spell takes the form of a cylinder 5 feet wide and 60 feet long that originates from you. All creatures directly hit must succeed on a Constitution saving throw, take radiant damage equal to 8 rolls of your martial die, and are blinded for 1 minute on a failed save, or unblinded and take half damage on a successful one. Starting at level 17 you can cast the solar barrage spell twice per dawn, and you can choose to cast the spell in the form of a sphere with a range of 45 meters that generates an explosion with a radius of 6 meters.

Level 17: Soul of the sun

By spending 3 ki points you can activate an aura of pure solar power that lasts 1 minute as a bonus action. Your body glows, generating sunlight for 30 feet around you, also dispelling magical darkness in this light, and dim light for an additional 30 feet. You can disable this light without needing a bonus action, the light automatically turns off when you are incapacitated. Whenever you hit a creature with an unarmed attack, you deal radiant damage equal to your Wisdom modifier. As long as you emit this light all attack rolls against you have disadvantage, you are immune to radiant damage. In this form solar muscles does not require ki points for activation. Starting at level 18, when you activate Greater Defense, you can activate this ability by spending 1 ki point, as part of the Greater Defense activation.