I wonder if this is technically possible? Make a coin with one billion APR staking returns. I'm thinking of a Peercoin fork for example where the staking returns were just set to an absurdly high level. I understand that something would have to be done to not hit integer limits, maybe there could be multiple tokens internally where each level of tokens is one billion times the value of the previous level.

In a country where staking income is taxed as capital gains before even selling, this would be instant financial suicide probably, if it held any value? Of course it would be problematic for exchanges as there can be only so many zeroes in their prices.