Wait what?
Not to get too off-topic, but Rimowa luggage is more durable than your average suitcase. Why do you think Aegean is not capable of transporting them?

If you truly want to avoid this, 'at all cost' maybe don't bring the laptop bag? I would say there is definitely a chance that they would ask you to check the extra bag. You shouldn't get any charge for this, but I have often seen them asking people to check their trolley bags.

I wouldn't be sure what the likelihood is, but I would say that it is definitely possible, and if you want to avoid at all costs, just showing up and hoping for the best does not seem like the choice I would make...