Re: Aikido against strong people...
I always tell folks that strength is never a disadvantage in a confrontation or daily life, but it can be a disadvantage in training. In a crisis, you are what you train not what you aspire to be.
If you regularly overcome poor technique or position with strength, you're technical skills won't grow and there is always someone stronger that will be impossible to defeat by mere strength. And more importantly, when a technique doesn't work in a crisis, you'll attempt to fix the problem with strength instead of flowing into a better position and technique.
I also believe very strongly (pun intended) that routinely using strength as an uke/tori to block technique even with good intentions isn't a good idea since it can train in reflexes to confront poor technique with tension and strength. In a crisis, instead of taking advantage of the poor technique to escape and reverse, you'll stand there immobile with a look of disdain until the guy stomps on your exposed knee. If you are not moving, you are a target.