Personally removing the offsite part is not that bad for me as my offsite/onsite ratio is not that much higher than the average one. Assuming that removing it would probably discourage current "leveraged" investors to stay, it's probably neutral, so OK.
However, there must be a cap on the fee, which I think should be 50%, that's already a crazy profit for the casino, especially combined with their own investment in the bankroll. To keep things easier I'd just leave the fee at 50% instead of using that new formula which would require investors to keep looking at how big the bankroll is. Also if the fee was dynamic, the max profit should be dynamic too in relation to the fee. Otherwise, imagine the extreme scenario in which the bankroll got to 9,000. Then the kelly would be very high unless the max bet is adjusted to the much lower expected value per bet for investors. The maximum profit should be 2*bankroll*(0.01*(1-fee)) so that expected bankroll growth is at least 0.
If 10,000 is the number that Devans doesn't want to reach, what I'd do in his situation is becoming more aggressive with the dilution fee, starting with 5%.
Capping the fee would defeat the purpose as it would no longer provide a disincentive to invest once the bankroll reaches 5,000 BTC.
As the commission is only charged on net profits, it doesn't affect the Kelly criterion. The optimal risk for the bankroll according to the Kelly criterion is 1% (the house edge) regardless of the commission rate.
Unfortunately the dilution fee on its own is not effective in capping the bankroll size. Since the beginning of this year, there has been a net divestment of ~750 BTC, i.e. overall investors divested 700 BTC more than they invested. Despite that, the bankroll has grown nearly 900 BTC since then.
So basically when we reach 10.000 btc, it's 100% loss for investors and 0% gain ?
If we get to that point :
- owner will get all the profit
- bankroll will fluctuate a bit between 10.000 btc and a bit lower when there is a swing downward and will recover to 10.000 slowly (due to a 99% commission on win). - reaching a 10k equilibrium
This also means new investors are screwing old one even more since in addition to dilution, they also increase the overall commission rate.
Nobody would invest money in something if they didn't stand to earn a profit, which is why the bankroll will never reach 10,000 BTC. In practice the bankroll will find an equilibrium at a much lower size where investors are content with the rate of return. For what it's worth this is already the case. All the dynamic commission does is nudge that point of equilibrium towards a smaller bankroll.
If decreasing liability for the investors money really is the main incentive here, why not discourage onsite investing and encourage offsite investing again?
Just a question, I don't know what would be the downside of making offsite investing possible again...
Having a large offsite bankroll can make the bankroll volatile. When an investor's onsite investment becomes too small to support their offsite investment they are margin-called, causing their offsite investment to be set to zero. As a result a lucky high roller might see the maximum profit collapse at the worst possible time, after they've just won a large amount.