Would it suffice to use a hive-usd value per week or even per month ... that does make it much easier than per instance to run a report for users who would want to use a potential product like that.

...

Holding stake isn't the taxable even its the selling of it ... maybe it's even the powering down? But I guess people do get interest from the blockchain from holding stake but that usually comes in the form of more stake if I'm not mistaken.
The question becomes do you count stake increasing events? Or just liquid token increasing events?

If so maybe @dan would consider changing settings to getting rewarded in HP only because some tax accountants would argue staked hive isn't a taxable event like getting liquid rewards. And when you power down is the taxable event.