We are using piCore for piCorePlayer with hundreds of users, many just pull the power to turn the player off. They have been doing this for 3 or 4 years and to-date we haven't had complaints about corrupted SD cards. I haven't seen one personally. After the initial setup we don't write to the SD card.
We use the standard setup with /opt and /home in RAM and haven't found it necessary to copy to RAM or unmount mmcblk0p2, though technically is the right thing to do.
So the standard setup has proven extremely reliable.
The other thing, if you somehow manage to corrupt the SD card, the image is so small it takes very little time to burn a new one, in our case less than 10 seconds. This is a feature that should be shouted from the roof tops.
Thanks for the info, this is a good thing to know.
My concern is not about the time it takes to create a new sd card but more about the reliability and the physical access : one of my RPi is used for local control of some equipment and is bundled inside of it. So its access is a bit annoying.