Well, I was able to get:
- root
- custom recovery
- Actual ICS play store.
I installed the v3 firmware... And then tried to follow some initial instructions to get the market to work, all to naught.
So, since I backed up everything anyway, decided to play with the root tool at http://forum.xda-developers.com/show....php?t=1886460
Using that tool's option #3 ("new standard root") I got root in no time. (Frightening how easy it was)
I then used william's old custom recovery installer form when I tried to play with CM10 it... No problem there.
Since I had already tried everything else, I tried flashing the 20120429 GAPPS since it was the closet to the time stamps on the version of the Google frameworks in /system/app. After the second reboot (maybe I wasn't patient enough the first time) I was able to get in and run the play store.
Now I can edit the fun permissions files to re-enable external SD card access, and have everything I need one this cheap tablet. Maybe I'll let my daughter take it to school now...