Thanks @Ashwin_DSA 

I started to test: changing the bronze layer from addNewColumns to rescure (schemaEvolutionMode) while still keeping the format setting of autoloader as.csv. Then processing the _rescued data at silver. 

Or, the last resort, having autoloader to use format text, then processing and extract columns at silver layer. 

I will need to do some testing to finalize which method is simpler.