What do you mean by broader definition options?
Coinprism includes a link in the transaction that issues an asset using an OP_RETURN output. The link can be user defined, however otherwise directs to a Coinprism hosted page that includes a "contract details" field. Of course, I can't speak for Bytas, though I think that this type of functionality could be valuable.
That said, I have significant problems with the way that Coinprism associates contract details with an asset. First, the definitions are centrally hosted, and can be changed at will. Second, an asset can't be verified to be legit if the URL becomes invalid at some point in time. Further, even if you select a custom URL, you're required to have the http:// and .com.
I think proper implementation of an asset definition at issuance should be the hash of the contract in the OP_RETURN output. Somebody really creative could even store the contract with Namecoin and indexed by the hash of the contract. This is probably just a pipedream of mine though.
I don't know how this is all directly applicable to ChromaWallet given the drastic differences in implementation.
Coinprism here. Normally, the asset definition is stored on the website of the issuer. When you buy an asset, you are trusting the good faith of the issuer anyway. Sure, the issuer could change the metadata hosted at that URL, but again he could just as well refuse to redeem your coins. The metadata doesn't really have any legal value, if you want it to have a legal value, you need to find a lawyer and have a proper contract drafted.
The fact that the metadata is stored on a "central" server is not actually an issue. Also, in theory, it is possible to put a magnet: url for the metadata, and host in on Bittorrent (though that is not implemented yet).