To clarify, in my proposal the long name wouldn't be changeable.
In the leave things mostly as they are scenerio, which is what I was describing above then the 'name space' would be able to change since it is just part of the asset description. The asset name is still the primary key and has to stay the same.
I can see the disadvantage of this where people can issue spam assets to 'typosquat' or even create duplicates of the same namespace. If it's not enforced by the protocol as you said, it's going to cause confusion.
The idea is that it is possible to implement name and category functionality without altering the protocol by making some filtration standards for indexing Assets, so an asset may be DKGCEWU (some unique 8 letter base_58 asset code or 'short name') ~ Gold Troy Ounce ~ ~ (issuer) ~ ~ (comment /pgp link) ~
of course one has to trust the issuer and check the link for the valid pgp signature, but once one has done this all the problems are gui / client problems, you could exclude the ability for someone else to create ~ Gold Troy Ounce ~ on the protocol level but then you are back to the original asset name problem. Instead you link the ~ Gold Troy Ounce ~ to the DKGCEWU that identifies the asset. Sure someone else can make a ~ Gold Troy Ounce ~ but it can easily be distinguished by the 'short name' as different.