Thanks for the suggestions, each of method has its own advantages.
A Map of names to id’s seems the best method so far, at least as the base. Its just a bit of a pain to manage.
These are the requirements i had in my head:
Need to manually define the data length of each property.
Need to manually define whether the property is savable.
Need to read/write properties very fast.
need to be able to rename properties
file encoder format must be flexible/changeable.
The file data will be used to store large amounts of data such as terrain/entire maps, and streamed over internet and decoded fast. For that reason save-games are not great.