Looking for a way to remote manage a completely headless system

You should try Remote Desktop (again). It will work fine on a system without a graphics adapter as confirmed by this Microsoft blog post:

"RDP plugs into the Windows graphics system the same way a real display driver does, except that, instead of being a driver for a physical video card, RDP is a virtual display driver".

From your comment:

...[M]y issue with [Remote Desktop]...is that the user account...is a under privileged user that has [its] password disabled to [permit] automatically login on the event of a power failure / reboot.

I understand the account doesn't have a password so that Windows can login to the account automatically, but this also prevents using the account for Remote Desktop due to the security policy preventing network connections using accounts with blank passwords.

This can easily be solved by assigning a password which will enable Remote Desktop for that account (after you add it to the Remote Desktop Users group). Then configure the computer to automatically logon using the account and it's password.

PowerShell has Enter-PSSession. It's going to take some work to get the computers to trust each other and configure Windows 7 for remote management but it's doable.