What about fill_vesting_withdraw ops? Should they count as a revenue source?

I guess but it's steem you already own, not revenue that's coming from new sources.

Also, on a small note, maybe you can use INSERT ... ON DUPLICATE KEY UPDATE ... syntax

I thought about it when coding but I figured that way was clearer for future use and one select call on a primary key on a table that got one row per day per account tracked is really not going to be a performance issue before a very long time.

Regarding the initial table creation, I would love to see a npm create_initial_table custom command to create the initial table.

Ah ! Good point ! I'll add that to a future version.