the reason why structure is optional, is to allow us to modify parameter options (label,...) without sending a mandatory structure
size-wise it doesn't make a difference for a valueupdate: structure needs to be either mandatory, or part of the value
if structure is optional, in theorie the structure coming with default-value, value and the structure option could conflict
therefore we conclude:
lets make structure mandatory: this avoids potential structure-conflicts and does not have a disadvantage for value-updates (only for parameter-option updates)
add to spec here: https://github.com/rabbitControl/RCP/blob/master/RCPValue.md#typedefinition-array