To reduce gas and storage, the protocol has currently designed to store the index of the premiumOptions[] & strikeOptions[] in the Vault structure.
This is too restrictive and may not be future proof.
One suggestion is to add another member unit8 premiumMultiplier (with default value of 1) in the Vault struct, and users can have combination of values of the
premiumMultiplier and premiumIndex to define more range of premium values if required.
Same suggestion applies for adding a multiplier for the strikeOptions[]
