InquisitiveCoder, I have to say that your "3 problems" merely represent your playing preferences and are by no means universal. "Nobody" wants to put time into creating a character that's going to be butchered?

FYI, there is an entire game built around the concept. It's quite popular too. Dungeon Crawl Classics from Goodman Games features a character creation system tgey call a character funnel. You build a number of zero level nobodies and run them through a starter adventure that kills most of them and then level up one of the survivors that seems interesting.

So, maybe refrain from shitting on someone's idea just because it doesn't appeal to you. Thanks.

Quote from Koren>>

"Nobody" wants to put time into creating a character that's going to be butchered?

I'm not talking about the character getting killed. Go back to what I wrote - I'm talking about the players being expected to put together 1st level characters that the DM will take home and nerf. That's why I said "Give your players their real options up front so they have real choices and play exactly what they build."

Also, you can have high-mortality dungeon crawls with level 1 characters. There's nothing about that style that necessitates level 0 characters. 1st level characters are notoriously easy to kill and Tomb of Annihilation has a "meatgrinder mode" that makes death saves easier to fail.

So, maybe refrain from shitting on someone's idea just because it doesn't appeal to you. Thanks.

@Koren.

The OP hasn't actually persuaded anyone to be involved in the project. His own son's response was "Why?"
Considering the playing preferences of your (potential) players is a key factor in running a successful adventure, and InquisitiveCoder was just re-iterating some of the points that have to be considered before investing hours of effort into something that may never be appreciated. Something that may well put a group of neophytes off the idea of roleplaying for ever....

You seem very insecure - perhaps that is why your post was so aggressive, and you felt the need to sink to coarse language at the end, demonstrating your inability to recognise that the vast majority of contributors to this forum do not use such vulgarities and are therefore unlikely to be impressed by it. (See the comment above - this is a related point, but I suspect that would go unrecognised by you too.)

If an idea can't survive a little poop from above, then it can't be a very good idea.

Anyway...

I see now the conflict of lvl 1 vs. lvl 0 characters here. Back to the original question of mechanical execution, this type of campaign would require an entirely new class based on reduced stats, minimal proficiencies, and unlimited growth potential. As stated, the Commoner option is probably the most viable. If you are looking for a way to execute on a case-by-case basis or create specific rules/modifications, I'm afraid the only way is trial-and-error.

The wonderful thing about DDB tbat I have seen is that people are generally open to experimentation. If you make the intent clear and everyone understands that rules are subject to change based on proposal and consensus, then you have the foundation to build any number of various campaign constructions. Communication is the bridge between your ideas and fruition.

A point of clarification... well, two. Edit: okay, three.

1. I don't mind people tearing up the idea. I appreciate the defense, but InquisitiveCoder and PlunderedTombs are welcome to their opinions. It is, after all, what I was seeking, eh? :)

2. The intent is not, and never has been, to put nerfed characters into an adventure and see how long it takes for them to die. The intent is, and always has been, to present interesting role-playing opportunities for players who want them, to invest in their character's origin and backstory, and play a little of what comes before first level. Then, and this would happen as part of the planned game, they would get to level 1 and proceed through the adventure. I have ideas sketched out through level 3 at this point. I'm not planning on putting nerfed characters into a meat grinder. That would be awful for everyone.

3. The biggest stumbling block you all have identified, and it is a big one, is that this feels like it will have to start out as a one-on-one role-playing scenario, whether that is a lot of backstory back and forth between the DM and each player, or actual role-playing/gaming to set them up. You're right, not every wizard is going to be able to have some macguffin that makes them a wizard. Some will have studied for years before getting to their first cantrip. But I think these are problems that are surmountable for players who want to develop characters in this way.

This may be a question of play style differences between me (and hopefully 3-4 others) and some of the commenters. Some of you can't imagine ever wanting to do something like this. I think it would be a cool avenue for storytelling. The Goodman Games example above sounds horrifying. A "character funnel" with what is essentially spinning blades of death at the small end? When I create a character, I use the mechanics to generate hooks for an interesting backstory, then jigger the mechanics to fit my ideas. Making mechanical characters just to try out this or that combination of tactics or spells has very little appeal to me. As they say, to each his or her own.

I *am* developing a comprehensive post I could use as a recruiting tool if I did this, and it is chock full of warnings about my play style, about what will happen to nerf a character, about what the zero level part will be like, examples of what a character's progression would be like... I just didn't put that all here because my original question was about the mechanics, not the idea. ;)

I apologize if I hit a nerve with my post, and for my poor choice if words. As I read the OP, he was looking for ideas on how to implement zero-level characters here pn DDB as a viable starting point for a 5E campaign. Instead of suggestions, I saw a lot of posts telling him it was s horrible idea. It's not, just maybe not right for a lot of players. I was trying to point that out. 

I've offered my thoughts and suggestions, so I guess at this point I'll leave you folks to gnaw at it. Happy gaming.

Thanks, Koren. I appreciate the intent of both the defense, and the apology. Yay for civility!