1. Ability to push/pull a range from a company-wide database, based on a (name,date) key. When you pull based on a (name,date) key, you get the first range with that name that was published on or before the date you specified. A dev team at the bank implemented this and people really loved it.
2. Versioning, but more for reasons of space than for having a "blame" feature. People use the same spreadsheet daily/weekly to create a report, so they have to save copies of the reports daily/weekly in case they need to reproduce the calculations from a particular report even though the differences from report to report were just minor tweaks. It wasn't uncommon for me to see spreadsheets that were > 100 MB, copied and saved daily.
3. Better explaining of formulas - you can ask Excel what cells reference another cell and it'll draw a bunch of arrows for you, but it still takes a lot of concentration to figure out why you're getting the number 4 in a cell when its references are many cells deep, spread across several worksheets. It would be nice if there was a clear way of explaining a cell's formula without having to navigate from worksheet to worksheet and actually hand-trace the references. Even collecting all of the references in one place and drawing out a tree of formulas would be an improvement.