I was writing everything in my mathematical report in "Times New Roman" font...
Suddenly I discovered that university requirement is "Arial" font. (I could have
had a spontaneous change of decision of my own as well, it's a user's right to
change font in entire document!) I changed the "default" style font easily, but
I had several hundreds of formulas (equations) in my document which were in
"Times New Roman". How do I correct all formulas in my document to another font?

It would be great if the user could select entire document or its part and run
some command to change formulas' style in the selection, including:
- font size
- percentages of sizes for indexed, limits, functions, operators, text, etc.
- fonts (separate settings for variables / functions / numbers / text / serif /
sans-serif / fixed)
- color


Also, it would be great to extend this feature to an option of that the formulas
could automatically change 
- their default font for numbers and variables and 
- their default size  
- their color
  to match the style of their surrounding text every time it changes.