Allow for equations using the equation editor to reference values of cells
The idea is that as users change the values of cells, the values within an equation object will change accordingly.
At first I didn't understand your idea because I didn't think that equation editor worked in Excel, but I see now that you can use equation editor if you insert a text box.
So yes, now that I understand your idea, this would be VERY useful functionality to have right inside Excel. This combined with a visual display of math formulas would blend the boundary between Excel and basic math analysis software.