1. We should write the bootstrapped pip to the same location that
we're installing the package to (so system global, user local or
current venv).

this makes sense for global and user installs, but not venv?
when you're in a venv, you're using the pip installed in that specific venv, not the bootstrap.

and just to confirm about user install bootstrapping, it would work like this?
- user1 happens to run "pip3 install --user django" as his first pip3 command
- the bootstrap installs pip to /home/user1/.local 
- thereafter, user1's executions of pip3 detects the importable pip in user local, and does no more bootstrapping
- user2 runs "pip3 install --user django" as his first pip3 command
- the bootstrap installs pip to /home/user2/.local
  ...

and if instead user1 ran "sudo pip install django" as his first command, pip get's installed globally.
and thereafter, all users would be using a global installed pip, no matter what they're first command was.

Marcus