Nice try 
But no attos this time…
Immutability seems to be a good intuition, but not only Chunk is immutable, also GraphEntry itself. So, it could be a link to other GraphEntry, but this is currently blocked. Not to mention, that linking to other GEs is possible through inputs and outputs. Or, in fact, to any other datatypes, like Scratchpad or Pointer, so mutable. But they are intended for other uses, so that would be some sort of hack. If someone tried to block linking to mutable types, it was not a success. But it successfully blocked linking to GEs without abusing inputs/outputs.
Yes, I wanted to keep token_id in content field, and it was an address of Chunk with TokenInfo data, so 32 bytes. As I’m becoming convinced, that it’s better to make squatting token ids impossible, I wanted token_id to be just genesis GE address. But I’ll probably stuff it into first input of every spend/GE
You could maybe kinda have the mutable GE by linking to Scratchpad/Pointer with one of inputs or outputs, or somehow use content as an index to derive full address?