Great post OP, reading this really gave me some great ideas for what I would like to see for Non Origin Characters. One of my favorite RPGs is Dragon Age Origins. If I were to equate your definitions to the origin stories in DA:O I would say they seem to fit the mold of Semi Custom Characters. I’m personally really quite fond of this type of character. I love the flexibility of being able to define our player character by their actions but still having a background to give our character a place in the world. My personal favorite origin in DA:O was the Dwarven Noble. I love how it introduced the dwarven culture, as well as the darkspawn threat and set up the political tensions over the succession to the throne. I loved how it established the world and your characters current place in it without establishing a personality.
Contrast this with Tav, waking up on the Nautiloid feels like starting DA:O with the joining ritual at Ostagar. It would be a similar feeling of being thrust into this extremely serious situation but without any build up for the player to care. Like yes you would care about surviving the present situation, but why should I care about my own character. DA:O’s origin stories give our characters motivations and histories that tie them to the world. Additionally they set up future personal stories and unique interactions with the main story. Trying to recruit the Dwarves feels so much more personal and interesting if you are returning as an outcast dwarven noble.
As such I’d love to see DA:O like Semi Custom Characters in BG3. I was mulling over some ideas and came up with 3 examples.
Elturel Refugee:
For this origin I imagine our character starting out in Elturel. It would take place after Elturel is returned to the Material Plane. You have yet to be reunited with your (friends/family/lover) but you heard that they have already left the city and are headed to Baldur's Gate so you decide to join one of the many caravans of refugees headed to BG as a guard. Some time after leaving the city you are attacked by goblins or bandits. This could serve as an introduction to combat prior to the Nautiloid that is more appropriate for a level 1 character which seems to be a complaint a few people have. After the combat encounter you could have a cutscene of your PC being abducted by the nautiloid which would serve to show how you got there. Additionally you could give enough exp during the origin story prior to the Nautiloid to get your character to level 2 which might make it seem a little more appropriate. This origin story could have some unique interactions with the refugees at the druids grove. And once you get to BG your personal quest could involve looking for your missing loved ones and helping out the other refugees.
Baldur’s Gate Flaming Fist:
For this origin I imagined our character is a fairly recently joined flaming fist member. Your captain assins you and your squad member to investigate some Dead Three suspected murders. You are sent to some slums and are attacked by thugs but they don’t seem to be related to the Dead Three. You then enter a building and after some searching you find some documents that mention something suspicious happening outside the city. Transition to a new area that was mentioned in the document. You and your squad are ambushed by Dead Three/Absolute cultists and you are knocked unconscious. Your eyes flutter open and you see the cultist leader talking to a mind flayer right before passing out again. This origin story could have some unique interactions once you return to Baldur's Gate assuming you were going to interact with the Flaming Fist at some point. Additionally once you get to Moonrise Towers you might see one of your previous squad mates is now a true soul and you might have the option to try and convince them to betray the cult of the absolute.
Harpers Initiate:
For this origin I imagine our character is a Harper Initiate that is sent along with a senior harper member to investigate a Selunite temple they haven’t heard from in some time. When you arrive at the temple it has been either taken over by bandits or low level monsters. After clearing out the mobs you look for clues and find some traces of Sharn members. This might be a little too similar to Grym Forge but I'm running out of ideas sorry. Not really sure how to transition this one to the nautiloid either but I was trying to hit each of the major plot threads so I wanted to include this one.
I’m sure GM4Him or Niara or any others way more creative than me could come up with some interesting premises.
The main goals of such a Origin System would be to give our player characters a place in the world, an introduction to one of the main plot threads and set up for a personal quest and personal interactions with characters in the world.