Hrm... How many hashes does one need before a minimum payout?
I've been working on this problem for about 6 months now, but my solution is just to let the site owner sell virtual items that have no lower cost except bandwidth or value (say like selling steam trading cards).
Do those Alt coins have such a low transaction fee that it would not cost people to mine?
Also I made an wordpress plug in that tracks by user for Coinhive if that's something you could use.
But if I could find a low transaction fee coin that I could put on a WooCommerce site then we got the holy coin. (If only IOTA would work)
It depends, for gridcoin 1000 hashes is enough for minimal payout, for dogecoin 500 000 hashes is 2 doge (but 1 doge will be comission), for bitcoin minimum 500 000 000 hashes, almost never.