http://www.sqlservercentral.com/stairway/105855/ answered a lot of concerns for me.
The gap for me was the way that user defined aggregates worked. http://www.sqlservercentral.com/articles/SQLCLR/71942/
I had hoped to make a lot of...

If you understand the limitations of table variables then you have a tool you understand. You will understand when they will cause problems and when they won't. I don't shy...

I am not optimistic.  Shadow IT presents immense risk from a data security and compliance perspective.  The problem is that Shadow IT is often sanctioned by people with spending authority...

Wait until i write up the experiment for which I went to all this trouble to build these functions.  All will become clear

There needs to be a training strategy with clearly stated goals, provision for training time and a plan to use those skills once the course is complete.
Without such thought...

I would be curious to know from those who have audit controls whether they are something formally recognised and supported.  I know of DBAs who maintain a log of queries...