Believe me, don't get me wrong, I would gladly trade 50% of my salary to work part time. But...

    That don’t need to spend lots of 
    time getting context. They can figure 
    out how to solve problems matching 
    your team’s coding style without 
    extra meetings.

I've worked a variety of enterprise-y developer jobs, and I don't find that to be the case at all. I mean, that context is the job.

Coding bits of functionality for an existing business is not a matter of "matching the team's coding style."

Heck, there are often not even engineering "problems" to "solve." It's a matter of figuring out integration with existing systems and processes, understanding the business itself, etc. That's why part-timers don't make sense. They can't just walk in, sit down, and code.

And if you could tee things up for them, to the point where they could just sit down and code, then 90% of the work is already done. And your part-time coder will take longer to deliver... why would management want to wait 2 weeks for a part time person to complete 40 hours of pure coding work, versus 1 week for a fulltimer?