I'm not an expert, but wouldn't capping the max profit (at 20%, 30% or even 50% of current bankroll) solve the issue?
What is the issue exactly?
Player being able to win almost entire bankroll in a single bet.
The investor can't have both increased expected value and profits AND remain risk adverse.
With SafeDice's setup (up to 10x kelly), you need to realize that it's favouring investors who prefer the former rather than the latter and really there's no problem with that.
You can't expect to have fast and steady profits without taking a risk of ruin. It's not designed this way. IMO, these investment options are quite attractive and should provide a good return, however people shouldn't be regarding these investments as can't lose investments expecting them to never break.
Investors shouldn't be putting more than what they can afford to lose in this (or any) bankroll and instead should be adjusting according to their preferred balance of tolerance of risk and profit sought.
It's not the kelly system. SD disregards the kelly system at higher bets and adjusts the house edge to compensate. That's the issue here.