I have thought for a long time that upcasting was an area with great untapped potential. By 'upcasting', of course, I mean the stuff some spells have listed under the "At Higher Levels" section.
I suspect that one concern the designers had about this was stepping on the toes of the sorcerers' metamagic feature. I don't want to do that, but I am very interested in expanding the upcasting options for everyone. What do y'all think are some good general options? I'd prefer things that apply reasonably to "all spells that meet requirements x, y, z" so you don't need to edit single spells in the book, just have a list of options.