I read with interest the thread about Aikido in real situations and that is what led me to this question - how can one make their Aikido work on someone with this natural size and strength?
This made me think about something that my sensei says from time to time: "'When' is most important. 'Where' comes next, and 'what' is last." That line tends to come out when he sees his students getting mired down in the 'what' -- the technique we're supposed to execute, the end result we're supposed to get to -- and putting the cart before the horse, so to speak. His point is that the timing is the most important thing, and next is position and orientation, and if you don't get those right, getting to the 'what' is difficult at best.
Applying that to a situation where your opponent (or partner) has great physical advantages over you, it seems to me that you don't neutralize that advantage by choosing the "right" technique -- it's got to be a matter of impeccable timing and tai sabaki, first and foremost. Those two things would constitute your
advantage in the situation, and if you can get them right, against a bigger and stronger opponent, you've got a chance of being able to use some technique effectively.