Structs/Traits already exist in some form that is not well defined yet, what you are describing is a generalization of what is happening with Ethereum right now, we have eth-block being a IPLD "Format", which is basically a struct with some particular characteristic where the parser instead of being written in a IPFS VM language, it is written and executed as part of the daemon.
The idea that you have described above or a subset of it, it's part of the plan!
Please do participate in the issue that I linked you to!
Structs/Traits already exist in some form that is not well defined yet, what you are describing is a generalization of what is happening with Ethereum right now, we have eth-block being a IPLD "Format", which is basically a struct with some particular characteristic where the parser instead of being written in a IPFS VM language, it is written and executed as part of the daemon.
The idea that you have described above or a subset of it, it's part of the plan!
Please do participate in the issue that I linked you to!