34K !!!
That explains why he kept quiet about it.
To keep within our 3 year target, he needs to payout approx
BTC218 per week.
With difficulty about to explode into orbit, if he hasn't got some bad boy ASICs in the pipeline, I think we can all scrub out this 3 year plan. More like 300 years.
Even with ASICs, it's very hard to do through mining if Bitcoin continues to gain popularity.
One thing that can be done is an option to convert the debt to other currencies. Basically Hash agrees to convert Alice's 100 BTC debt to 1000 EUR. Alice buys 100 BTC with her 1000 EUR today, thereby making her initial 'BTC' investment whole. She then converts every payment she gets from Hash to EUR upon receipt. The obligation ends when Alice has been paid 1000 EUR.
If the payment will be made through mining, this will be the only approach to make it viable. Of course Alice will get more than 100 BTC if EUR/BTC exchange rate goes down, but it doesn't affect Hash because he will also be making more by mining.
The pro rata algorithm can remain based on the conventional "remaining BTC" balance and the converted account can be checked in parallel. This way, converting your account to an inflating currency would be favored.