They should instead give you a one-time username change with 3 new similar username ideas where it's not inappropriate.

I think they already do this, but only if the account isn't like 2 days old or something and doesn't have any projects

They ban them and allow them to make a new account (which they never do for normal bans as it is ban evasion) if it's clear they aren't trolling and made a mistake. However, if you contact them asking for a username change, I'm assuming they will unban you too.
They will allow their username to be changed if it:
- breaks the community guidelines
- causes gender dysphoria
- contains personal information (falls under breaks the community guidelines but it is pretty important to mention)

So pretty much this suggestion kind of exists?

YtArie5 wrote:

(#2)
I think they already do this

randomguy3513 wrote:

(#3)
So pretty much this suggestion kind of exists?

Yeah this is already long implemented.
EDIT: Atleast from what I remember, can't give examples since that'd be gossip even if there's evidence to support the past username.