Import independent Python package as if importing subpackage

Question

Problem

I have a fairly large package that is structured as follows:

package
  subpackage1
    __init__.py
    subsubpackages1
    modules1.py
    ...
  subpackage2
    __init__.py
    subsubpackages2
    modules2.py
    ...
  subpackage3
    ...

Now I'd like to split off subpackage2 into another repository as an independent package (let's call it new_package). However, I still need backwards compatibility with present code which imports as a subpackage, e.g.:

import package.subpackage2.modules2
from package.subpackage2 import modules2
import package.subpackage2.subsubpackages2.<and_so_on>

should still work, without the need to change all existing code to

import new_package.modules2
from new_package import modules2
import new_package.subsubpackages2.<and_so_on>

Possible solutions

The straightforward way would be to create a new subpackage2 in place, which would import from new_package, but that would not work for full import statements as they operate on the full package/module names.

I also thought about editing the sys.modules dict after importing new_package, but to my understanding each individual module would have to be accounted for, which would require all submodules of new_package to be imported at that point (which would also be undesirable).

Question

Since I'm not very familiar with the inner workings of importing packages: Is there any best-practice (or generally better) way of how to accomplish this? Would the procedure outlined above work reliably in principle?