Between the Hero books and the other players (such as those on this board) plus my own ingenuity, there aren't many effects left that I couldn't simulate. Having said that, here are the ones I tend to think people might like to see:
Making a character "Evil" - One of those great conventions of comics is turning a hero against his friends through use of powers. Mind control is generally intended for creating specific commands. Perhaps there's a good "transformation" type effect for this?
I think the book could benefit from a list of "side effects" (As in the Limitation). It seems to be one of the more under-used limitations, and a quick list of things (Power also catches attacker on fire, Power causes dizziness, etc.) and their worth might be useful to someone slapping together a new power.
I know we all love math (Yes, that's sarcasm). I think 1st or 2nd edition hero had a chart for calculating costs without a calculator? You know: You cross-index the active cost with the total limitation and it gives you a real cost. In this world of calculators it may be obsolete now, but I just know I hate carrying around a calculator.
How about a good, solid, comprehensive list of special effects. I know it's impossible to get them all (which is why its so fun to make powers) but wouldn't it be nice to have your player who is trying to come up with a concept turn to page 84 and look through a list (Ice, Fire, Electrical, etc.) to get ideas?
I hope something in there is useful to you. And I am looking forward to seeing this book more so than any other book you've put out (w/ the exception of 5e).
Thanks for listening to your customers.
Blue