The airline may have union contracts, employment conditions, or contracts with baggage handling services that limit the weight it can allow. For example, it may require employees in certain jobs to be capable of lifting X pounds, test for that during hiring, and limit bags to weighing no more than X.
You can limit yourself to carrying one very heavy bag, but check two bags.
Buy a really good hard sided suitcase that can stand being in an aircraft hold without being completely full. Also buy a foldable duffle bag. Label both.
Pack everything, including the duffle bag, inside the suitcase. Shortly before reaching baggage check, after you have a cart, move a planned set of heavy items, sufficient to bring its weight under the stated weight limit, from the suitcase to the duffle. Check in both the suitcase and the duffle bag.
At the other end, at baggage claim, put the duffle and its contents back in the suitcase.
Whenever you are doing the carrying there is one very heavy suitcase. When the airline is doing the carrying there are two bags, each under the airline's weight limit.