Yea Coinbase btc being hacked or quantum (technical black swan) breaking bitcoin are really the main risks imo.

If it continues to exist MSTR will continue to have demand for their stock which means they can pay the preferred share yield. Eventually I think they become a BTC bank

All these products are more or less the same mechanism. Get a lot of money now to buy BTC in the moment at the expense of paying fiat interest perpetually into the future.