The TokenScript holding token property defines the token contract to which the script refers to, and to what other contracts that token interacts with and those interaction rules.
Currently, without a holding token the script is meaningless; the wallet and website render token views and allow interaction via the wallet based on the script of the corresponding holding token.
Would this always be the case? Is there any value in having a script that doesn't have a holding token; eg some sort of library? Perhaps a set of standard ERC20/721 functions could be defined so they don't always need to be copy/pasted into the scripts.
In this case we'd need some additional abstraction syntax.