Even if you did the more extreme version ( stop all new investments) the bankroll would continue to increase by the investor profit (minus divestments). Investor profit over the last 90 days has been 533.50 BTC, which is an insane amount. That's literally like $100k/day average. I assume Daniel is in the position where the bankroll has become so big, that the only thing that happens by it increasing is increasing his liability.
But if you think of it though, it's actually a pretty clever idea. I think it'll become the standard way of doing bankroll commissions in the future. Basically Daniel is running a sort of auction, where investors are basically bidding against each other to provide the bankroll bustabit needs. (Although for the record, I don't think a linear relationship is the most optimal way to model it, and I would've pegged it against USD or something a bit more elegant than a fixed number like the largest bet in the last 3 months)
It's evident the bankroll would increase much more slowly if people were no longer allowed to increase their investment, or if there was a higher dilution fee for joining (which, as I said, I would be fine with going partially or even fully to Daniel).
People don't just let their investment accumulate, they withdraw part of their winnings to spend or invest in other places.
Removing the offsite balance is just a way to decrease expected returns for current investors while increasing it for new ones, as they end up with a higher percentage of the bankroll by investing the same amount. It doesn't even fix the supposed problem of the bankroll being too big, as the casino doesn't really have those offsite Bitcoins anyway. The casino doesn't have to worry about the offsite bankroll being stolen or whatever...
This change only makes sense to me if Daniel wants to increase his own investment in the platform, but even if that was the case this doesn't seem like the optimal way to do it.
I think the fairest and most coherent way to limit further investments is increasing the dilution fee, which is something that hasn't been tried as it's been stuck at the same percentage for a long time.
Talking about the last 90 days profits is unfair, you know that particular time frame was especially favourable to investors. Long-term expected returns are lower than that.