OP: I think introducing volatility (which you can just model with one percentage variable and a sinusoidal multiplier based on this: 100% volatility means if your "real" balance was going to be $100 today, it varies between $0 and $200 ; 10% volatility means you're fluctuating between $90 and $110) is also a good idea in teaching kids to refrain from the impulse of withdrawing the money just because today's daily gain is in the red.
Another add to the feature request list :)
The biggest challenge with pensions is convincing people in their 20s to invest in high risk/high return investments. This is usually the right strategy because of the long time horizon of several decades until they will need to crystallise losses/gains.
However if they see their pension balance fall in a big correction, they can panic and move to less volatile investments, thus reducing their long term gains.
You can theorize all you want but the best way to learn to cope with this is for it to happen to you so it would be great to include it in the simulation!