Just a suggestion, but if you do try it I would be interested in the result.
On the next training opportunity with this person, as uke, do your very best to follow them during every moment of the waza very closely. Try to "match" every movement they make. If they step out to the right when you are holding their right hand with your left, match them with enough energy so that they don't have the opportunity to over power or drag you. As you do this, keep your left hand ready on your centerline. See if following them closely leaves any openingings for you to use your other hand offensively.
Do not strike them even if the opening is there...just note what happens and what you feel is available, and think about how to use it.
If he is doing iriminage, when they enter strongly, stay focused on him, do not flinch...and instead of letting them move you, move yourself into the position they are going for, and as they throw, see if there is an opening as you let them take you over to grab their elbow and throw them instead.
If you find a lot of openings in their waza, you are probably correct, they are using a lot of strength. One way to deal with that is to continue to polish your ukemi by following them very closely, never lettting them get ahead of you, never allowing them to put you in a position to surprise you or hurt you. And it will teach you a LOT about one style of ukemi often seen in aikido.
They may eventually ask for you to resist more...which will say a lot as well...
Ron (stay safe)