Best way to bulk process Excel to JSON for each column in a spreadsheet, where each JSON document must contain a common ID column and a unique column

I am in the process of converting a large Excel file to separate JSON documents for each column in the Excel, keeping a common ID column that each JSON document must contain. The hard way of doing things is using an AttributeKeeper to preserve the common ID column that I need and the specific column that I want to make a JSON document for, with a separate writer for each JSON document. Is there an easier way to do this, similar to a Fanout but instead of grouping by rows of similar feature types I can do it by column?