Instead of making the Excel writer even more complex, we should move to an Excel styler transformer that allows for setting the output style for each record (feature/row/cell) and the whole sheet, separately from the writer and entirely dynamically, based on attributes.
This should be similar to transformers like PDFStyler, ChartGenerator, HTMLReportGenerator etc. and allow for settings like font, colors, alignment, formatting, cell protection, formulae, borders, conditional formatting, cell validation/dropdowns, filtering, inserting images, transposing, pivot tables, hyperlinks etc. There could be an Excel-style table in the transformer that allows to assign an attribute to each cell and make the above settings based on other attributes.
There are already a number of ideas around regarding Excel that could be united in this solution (filters, styles, fonts, template).
