You are free to use BytesType if you want, but adding meaningful types has the advantage of adding a checked documentation of what is stored in your CF. Or in other words:
Would that do any harm or are there any downsides, if I store columns with composite names or Integer type names in a column family with bytesType comparator & validator. I have observed that bytesType comparator would also sort the integer named columns in similar fashion as done by IntegerType comparator, so why should I just lock my CF to just store Integer or composite named columns, would be good if I could just mix different datatypes in same column family, No !?