To be a little more constructive:

I suggest instead of the "difficulty" screen that shows up when you start the game, you could add a few more options. Starting with the easiest to implement (least amount of coding time):
1) Point Buy setting. Have it initially set to 27 with a "warning" that if you decrease the number, the game will have increased difficulty relative to the difficulty setting that is chosen and if you increase the number, the game will have a decreased difficulty relative to the setting. I'd also add the option to apply a Point Buy setting (not necessarily the same as that of the main character) to Origin characters if you respec. You should also be able to spend 3 points to increase to 16 or 17 and 4 points to increase to 18.
2) Randomized attribute toggle. I guess it would be easiest to randomize and set point buy to 0. That would make it unnecessary to change the character creation screen, but I think that's fine because if you were just planning to reroll until you got what you wanted, you could set point buy to whatever you wanted instead. You can also have more than one randomization option (e.g., 3d6 for "hard", 4d6 for "normal", and 5d6 or more for "easy").
3) Bonus Feats selector. I would include an option to gain a Bonus Feat at each Level or every other Level, as well.
4) Unlock Level Cap. The easy version would allow you to advance beyond 12th Level only if you multiclass. I don't think this one matters much because 12th Level is close to endgame anyway, but it would be easy to implement.
5) Additional custom character toggle (at least so you could have two custom characters and leave a couple of slots open for vessels or origin characters). There is space for one more custom character in the mindflayer ship without preventing Lae'zel and Shadowheart from joining. Ideally, the custom character would also get a point buy and/or randomized attribute toggle because some players might want their "main character" to have better attributes.
6) Additional custom character numerical selector. There are several places where you could meet a custom character, such as "on the beach," "when you first make camp", "in a jail cell," "left for dead" (e.g., with the other bodies in front of the first goblin village), "dead" (a body pretty much anywhere you might find a dead body and that can be raised with a revivify scroll, such as in the place where you meet Withers), or "wandering around or investigating a location". With a little more effort, you could find your third custom party member in a location that depends on background or class, such as a Sorcerer or Wizard investigating the Harper site outside the Druid Grove, a Cleric or Paladin who is dead in Withers' room or the owlbear lair, a Druid or Ranger who is mingling with the Druids and is interested in joining your quest, a Rogue or Warlock is in the jail cell in the Druid Grove, a Fighter or Monk is left for dead outside the Goblin Village among the dead bodies, a Bard who is trying to help the Tiefling Bard at the Grove when you show up, etc. If you have two custom characters that might show up in the same place, you can have one of them just show up when you make camp.
7) Open a full character creation screen when you respec origin characters. Vessels, too, I guess, but I doubt anyone will use vessels if you can have custom characters.
8) Increased party size toggle. I don't see much reason to go beyond 5 characters, though I know some players might like that. At the very least, an increased party size toggle would allow you to have 4 custom characters (single or multiplayer) and one origin tagging along.

With these changes, you could probably make all difficulties Tactician and rely on the player to choose how easy the game is by giving themselves more attributes or feats. I estimate about +10 Point Buy drops difficulty by 1 (so if you were on Tactician with +10 Point Buy, that is the equivalent of "Balanced", and with +20 Point Buy, "Story").