Since System.String is being mapped to CHARACTER, most of the functionalities that it provides are now obstructed.
Anything particular you are missing?
I've experienced that those that I really need are available as native ABL functions. So not really missing for me.
You may try reflection, wrapped in an ABL class Or create a wrapper class in C# and reference that from the ABL.
.NET objects are inherently "fluent" which means you can keep chaining endlessly in one line of code. The CHARACTER mapping of System.String breaks this pattern.