I would like to propose a new API. The signature would look like this.
RexxThreadContext getRexxThreadContext(int thrdId);
When supplied with the thread ID it would return the associated RexxThreadContext. This API would allow classic Rexx APIs (exits, subcommands) to access the new oo APIs available in ooRexx 4.0. In fact, the proposed API could be made simpler by eliminating the thread ID argument and having the API use the caller's thread ID for the search.
Once the caller has the RexxThreadContext it could use all the new oo APIs. This would allow the classic subcommand environment to manipulate things like arrays, etc.