In this case, you'd probably have to create a class method in ObjectScript that changes the namespace, then call it using classMethodVoid() from the IRIS native SDK. But you'd have to make sure the necessary class method exists in all of the namespaces you want to change to and from, including %SYS.
I just now took a closer look at this because of a comment made on one of my ideas on the idea portal, and that's great news for us! Our software is an ERP system, and we have some customers who have multiple locations that they sell things out of. We generally have them share one code database, but different global databases. The old way, where it stored the table tuning statistics with the code, made it unusable for us because each of those locations would have different orders, invoices, customers, etc., so tuning the table would help one namespace and potentially harm the others!
Your NewsGetItem method has two parameters, version and id, but the route you have defined for it only has one parameter, id. The parameter lists need to match up and be in the same order. Try taking the version parameter our of the NewsGetItem class method.