There's nothing marxist about it. All investments carry risk. All of them. That's capitalism 101. The regulatory question is how an institution is required to book its risks. Banks don't typically buy lottery tickets because people actually understand the risks involved and the bank management would have its head handed to it. Call the "lottery ticket" a MBS and instead of a drawing you have some obscure model of credit risk and people think its a sure thing when it isn't.
I'm perfectly fine with a bank owning securitized debt instruments or other ephemeral assets. Where it gets messed up is when the instruments are considered to be capital instead of potential capital. You want to own MBS or other CDOs - great. Only the actual cash flow from the assets can be counted as capital for reserve requirements and not whatever its potential may or may not be.
The nature of private property and free markets, along with basic reason move people to mitigate risk. As I said, the most critical aspect of this kind of asset is cash flow, not the underlying value of the asset itself.
For example you purchase RE for $1 million. It cash flows positively to the tune of $6000/month after Principal, Interest, Taxes, Insurance (PITI). Due to some government regulation you are forced to value the property at $0. What happened?
From the banks perspective nothing as long as you conform to your loan terms. They don't do interim appraisals until it is time to refinance the property. These flows are easily valued and have been for a long time. It is not a confusing process.
The Marxist part of your analogy is this statement: Lets say a bank buys a bunch of lottery tickets.
No business person gambles. Marxists present the free market as a gamble. All life is full of risks and the best way to mitigate risk is through the free enterprise system. The alternative, which Marxists want and prefer, is government intervention, hence government control, hence our current financial crisis.
More of the same.
BTW here's a quote for you: Gambling is a tax on ignorance - Warren Buffet