Hi John,
The most elegant solution would be to create a custom assertion using the SDK:
https://docops.ca.com/devtest-solutions/10-3/en/using/using-the-sdk/extending-assertions
That will put all of your logic into a jar file - no need to copy/paste a script. Any changes you make to the code would automatically update all of your assertion instances as soon as the new jar is deployed.
Alternatively, if you're not comfortable using the DevTest API, you can create a Java method outside of the SDK framework. If you put it in a jar and drop it into hotDeploy, you can invoke the method from anywhere. You'd still use a scripted assertion, but it'd simply look like this:
return com.mycompany.devtest.MyCoolAssertion();
You'd get the same benefits as extending the DevTest API - it's just not quite as pretty.
--Mike