Let's say I ran a campaign and you played in it. Your character made it to epic levels in that campaign and made a lasting impact on the world.
Different players have different sensitivities. For example, I am fine with playful, good natured flirting, but an other player who comes from a different experience might have a legitimate problem with that. On the other hand, I come from a minority religious tradition, and am highly sensitive to religious coercion. Things that might not be on the radar of others might be a legitimate problem for me. Because of family, I am also sensitive about whether LGBTQ characters are presented respectfully − and having gay characters and then killing them off would definitely get my attention and if habitual definitely be a problem.
So, you are asking about me as a player personally.
My character is Epic Tier, say, "level 22" (level 20 with two Epic Boons).
I'm now running a new campaign set in the same world, taking place after the game you played in. You've decided for whatever reasons to not participate in this new game.
You've told me you don't want your old epic level character to be used as an NPC in the new game. I really like the world building we did and want to build on it, and make it central to the new plot.
Again, you are asking me personally.
My view is:
The player "owns" the character, and the DM "owns" the setting. There are places that genuinely overlap both character and setting. These overlaps are situations that "you and your DM agree on".
Obviously after you've already said you don't want the character to be an NPC, doing so despite your wishes would be rude. I'm just curious what would be acceptable.
So, say my Epic Tier character has founded a new Druid Circle or Wizard School, or acquired a "divine portfolio". These are clearly setting features.
If my character is no longer around to influence these setting features, then they by default also already belong to the DM.
So. Leave the player character alone, but any setting features are fair game, such as a new NPC continuing on the Druid Circle or Wizard School, or divine portfolio.
Would making an NPC that's your character, but not your character be equally rude? (For example, like a grocery store generic brand level knock-off. Honey-O's or the like.)
Neither I as a DM or any of my DMs would be mean-spirited about it. But the world can continue to turn in the absence of a character.
I would create an NPC to take over a setting institution. I would also let the player know what is going on.
Would making a new NPC that is distinct from your character, but essentially takes the place of you character be acceptable? (For example a new and distinct character, that happens to just get the credit for all of your character's achievements and becomes the new face to represent the world building that was done in the prior campaign.)
Yes.
Or should I just instead never run Campaign 2.0, just in case I later decide I'd like to run Campaign 1.5 where we pick up the story from the first campaign, and you also happen to play in this one?
Players own characters. Players dont own settings. The campaign continues with or without a specific character.