Here's my attempt:

      ~/Code/local/hn ································ at  09:14:14
     python3 hn_example.py       
    Hello Joe
    Hello Sue

      ~/Code/local/hn ································ at  09:14:16
     cat hn_example.py greeter.py
    ───────┬───────────────────────────────────────────────────────────
           │ File: hn_example.py
    ───────┼───────────────────────────────────────────────────────────
       1   │ import sys
       2   │ from importlib.util import find_spec, module_from_spec
       3   │ 
       4   │ def encapsulate(mod):
       5   │     s = find_spec(mod)
       6   │     m = module_from_spec(s)
       7   │     s.loader.exec_module(m)
       8   │     return m
       9   │ 
      10   │ greet1 = encapsulate("greeter")
      11   │ greet2 = encapsulate("greeter")
      12   │ 
      13   │ greet1.name = 'Joe'
      14   │ greet2.name = 'Sue'
      15   │ 
      16   │ greet1.greet()
      17   │ greet2.greet()
    ───────┴───────────────────────────────────────────────────────────
    ───────┬───────────────────────────────────────────────────────────
           │ File: greeter.py
    ───────┼───────────────────────────────────────────────────────────
       1   │ name = 'nobody'
       2   │     
       3   │ def greet():
       4   │     print ('Hello '+name)
    ───────┴───────────────────────────────────────────────────────────

I differ from your syntax by passing string parameters on (your) line 3 & 4 (my line 10 & 11).

I think this isn't a good idea though, i'd lookup __slots__ if leanness is an issue.