a) A full set of scientific fonts. Mathcad has always claimed to be create calculations like a book. This claim has stretched the imagination for 23 years. including over bar = mean, over dot = first derivative, double over dot = second derivative etc
c) Collapsible all formulae in one go to make the output look like a spreadsheet. Most box tickers are only ever interested in a simple list of results.
d) Split screen like Word and Excel (requested above)