The reason new features, and subsequently new parameters, haven't been added to CB Activity is those parameters need to be added to 5 different locations, have different parameter name syntaxes, and have to all be tested individually. So basically adding a new feature is days of just adding what should be a simple 1-2 lines of code. The code bloat has gotten so out of control with what features are already there it's becoming unmaintainable so the rewrite needs to happen before I can add more features.
My plan is to handle the storage rewrite of CB Activity before adding new features. The storage rewrite will move all CB Activity parameters under a single management page. They'll all be exclusively in CB Activity > Streams. This means activity streams will actually be stored in the database, can be rebuilt from their stream ids easily (this will allow sharing of activity links externally), and will allow making activity specific to a stream id. This brings a massive amount of improvements, but it too is a lot of work.
After CB Privacy release (6.2.0) and after CB Field Groups release (2.0.0) I will begin work on the storage rewrites for CB Activity and can then start adding a lot more new features. I don't have a time frame for this, but CB Privacy 6.2.0 is almost done. I figure maybe a month tops before both are finished and released, but depends on what kind of issues I run into during development and testing.
There is no way to add asset excluding at this time as the database queries just don't support that behavior in CB Activity right now.