Update!
As an alternative, I'm now considering generating full merit histories for all users weekly instead of "on demand", but I'll need bigger file hosting.
I just did this, it didn't take that much storage after all.
Example:
http://loycevsbasement.privatedns.org/Merit/history/459836.html is my full history. Change the userID to any other user that has either received or sent merit. Each user mentioned on the link has a link to his own history.