"You mean kind of like a big butcher block... you know they say that's how block planes got their name: from smoothing end-grain butcher blocks."

Yah that's it. It's not an ideal target but it would due for awhile. Most of my cut offs are pretty well dried by now so I don't think they would move around to much. As for the end grain soaking up water you need to paint the bulls eye on it any way, that would help.
kfhines