Option 3.5, very low overhead but user-dependent:
Submit your completion to https://github.com/zsh-users/zsh-completions

Like the others, this is not an optimal solutoin, but a lot of
frameworks include this repository in their fpath, and a lot of users do
as well, so this will get pretty much everyone with a configuration more
complex than zsh-newuser-install.

To cover a maximum number of use cases, you could always go for multiple
options, 1+3.5 sounds like a good candidate to me.

 - V