2 different topics here.
1) Doing Aikido against strong people.
2) Strong people doing Aikido.
Regarding 1:- obviously we all want to enjoy ourselves when we train - but enjoyment is relative. Every high grade in any art (no, I don't generalise..I've actually asked everyone in every art) will tell you that to improve you have to take the horrible
practices. The ones you don't enjoy, the people who are to awkward, slow, strong, sneaky to long a reach, too low a centre or just downright humiliating. That's where the gold is, there's the mountain you keep talking about climbing is. Try, fail, try, fail, try, fail. The very definition of a good practice. "What did you learn tonight?" "I have no idea...just lots of things that don't work, but hey I narrowed it down some more." To smooth something rough takes a lot of abrasion.
(On another level we need many different kinds of practice though)
Regarding 2:- You've all got grips that could crush a cow's leg.