I am not sure that something on chain can be time stamped out since it is locked in a block. The idea is to make locked block immutable.

Custom JSON does present some thing interesting. Does that block the chain? I guess it is a lot less bloat than messages but still will add to it.

Of course, is the desire to have the chain used? We see scaling being done to ensure that the chain can handle more (for less money). Isnt the idea to keep things growing?

I understand there will come a time where cost might be prohibitive.