Chris:

The real problem is that it isn't the "test suite" that spawns the processes, the tests invoke product code, and the product code spawns Python.  So modifying the Python-spawning really means modifying the product code to do something different under coverage, which most developers (rightfully) won't want to do.

My preference is not to assume a particular style of spawning subprocesses, since coverage.py tried quite hard to be applicable to any Python project.