For account/channel/oracle/contract we surly validate the hash value.
IPv4 uses 4 bytes, IPv16 uses 16 bytes.
If we figure out aggressive pricing that will compensate cost of in-tree memory, it’s fine to make it much bigger.
I started with proposal for very high level standard: AEX-draft 12 off chain state - #4 by robert
In general I think, tho, that AENS is not right solution for external data.
You can do it with spend transaction body and index it in 3rd party systems.
AENS, tho, would guarantee uniqueness of an entry.