That was an excellent description. My question, understanding your explanation, I can see where the price of the bond drives how much is left over to buy the options and how the caps and participation rates are pegged initially, but how could a scenario present itself that an in force policy could have higher credit rates in the future.
Here are a two quick examples:
Bailout cap: company issues new contracts at lower levels than current in-force contracts to prevent the loss assets from exercising the bailout provision.
Guaranteed minimum caps: think of fixed contracts 5 or 10 years ago that had a 3% floor. Currently the carriers cannot make enough profit by offering a 3% floor so they squeeze out another 1-1.5%. This example translates to FIAs that have higher minimum part. rates/spreads/caps.