I want to create a new sub-class for Bards as a new college called the College of Puppetry; OR I might just brew a separate class called Puppeteer.

I've done some research and have found some homebrewed stuff that is pretty good but not quite what I'm looking for. They are either too powerful or ghoulish.

Problem is, see, is that I am a puppeteer irl and have a good understanding of what this should look like. I think I can improve on them.

I know that I can just go and create whatever I want in private, as long as it is good with my fellow players and DM, but I really would like to publish it here. I think people could have a lot of fun with it. I've made it pretty detailed and easy to understand.

I don't want to plagiarize anyone but I like what they've done and want to include it, with my alterations.

I've not played in a long while and haven't ever been part of the online community. I'm looking for advice on what the norms are for improving on someone else's work and publishing it here.

Thanks!

Legally, you are able to copy and modify other people's homebrew on DNDBeyond. However, you should probably ask the creators if they are still active on DNDBeyond. If they aren't, I would say you can just take it as long as you modify it sufficiently. 

Give credit. If it's published material you can quote it here or provide a link. Either way, acknowledge who created it and be clear what's yours and what isn't.

Yeah, I think it is fine as long as you provide credit or ask the creators first. 

First off, you should ask the mods to move this thread to the homebrew discussion thread.  You do that by "reporting" yourself with the little flag icon and then click "wrong forum" in the dropdown and then type "Homebrew" in the field.  It's not that asking your question here is wrong but you're more likely to get the attention of folks in a homebrew mindset, that balances well with the game.

Second, making an independent puppeteer class is something you could do, but you wouldn't be able to make it on D&D Beyond's character builder (which is sort of the point for this site).  For homebrew, D&D Beyond only supports subclasses of official classes.  People could talk about it here, but you won't be able to put it into the D&D Beyond Homebrew system.  I like the idea of a College of Puppety for Bards.  I could see a very specialized form of Artificer too.  

The big thing to do for someone new to 5e would be to study how the core classes (Bard and possibly Artificer) introduce subclass features as the character progresses.  Doing a survey of the class's official subclasses will give you a sense of how much you can do within a subclass etc.  And also you can decide which aspects of puppetry will be class features and which will be spell-based magic.  Puppet related magic items....

I used to know a few dedicated puppeteers as well as performers who incorporate puppets into their work, and in another life would often use some essays on puppetry when I used to teach (I remember Kleist's "On the Marionette" theater from the 1700s, and would often read those in conjunction with I think something Brecht wrote and some other early 20th century theater experimenters).  I've never thought of puppets as an avenue to explore in D&D, but your post got my imagination going.

As far as taking existent homebrew and evolving them, I'm not sure what other home brewers think of it.  I think it only because really problematic if your using others work for commercial gain.

Lastly, integrating expertise as a subject matter expert into a game is a balancing act.  There's a lot of folks with varying degrees of expertise in various things and find the way their TTRPG handles them lacking so tries to improve upon it.  This can get dicey and crunchy real quick where your expertise blinds you to how workable the systems you're layering over the game actually are or are not.  But as I said, the homebrew community is pretty supportive and I'm sure there will be people interested in pushing this idea.