It's the same old story on all new aircrafts. Weight is always a problem. One pound less will always mean one pound less of a problem.
As long as the plane isn't finished there are small battles going on. Some engineers want "their systems" to be stronger, more capable, have more redundancies etc. Other engineers are pulling the other way and watching over the weight. It is all compromises, compromises and even more compromises.
It is completely false to believe that just installing more engine thrust can compensate. An airliner is structurally built up to accept a max take-off weight. Every pound more structure weight means one pound less payload or fuel capacity. And it means that until the plane is beercanned it must haul along that pound and burn many extra pounds of fuel doing that.
One day the battles will end, the plane has been built, ready for flight and has been certified. Then future modifications including weight saving measures will call for a new certification program.
There may be a "political problem" as well. When you sell an untested aircraft, then you will guarantee the customer some minimum performance figures, including a max empty weight. If the plane ends up slightly heavier than that, then the sales contract will most certainly state some compensation figures. For instance when the
MD-11 was introduced it fell badly victim to such things, mostly on fuel burn figures.