At the end of the day, doesn't matter if it is a good idea or a bad idea, yolodice should have ETH investment not just because it would be profitable for the casino but it would be profitable for the investors as well. Think of a situation where you would be capable of investing into yolodice and also stake at the same time, you would make a ton of money. Plus ethereum is the second biggest coin in the world right now behind bitcoin, which means if you have an option to invest ETH it would get so much more attention than any other coin except bitcoin.
This is why it will probably have a huuuuge bankroll as well and when you have huuuuge bankroll you will have a higher max bet chance as well which means a bigger chance of whales coming in and losing a ton of money here as well (even maybe on other coins too).
Things are not that easy, yolodice barely brought bank investment to their website, do you really think that yolodice would be easily implement something that would allow you to both have a bankroll here but at the same time stake your eth and make profit in both ways?
I am not saying it is impossible but for a website that barely got the investment part back on, helping others to also stake as well as invest to bankroll would be too much of a difficulty on the development part of the situation. However without that, it would mean that yolodice could stake on your behalf and get all the staking profits from it if you just invest and not get any staking in return, which means yolodice would make unfair profit.
Hence, they either going to do something that is unfair, or just nothing at all, I rather the nothing at all one.