> 7 kg is laughably little, a standard cabin bag already weighs 2
One thing that I have done is move from roller luggage to a travel backpack. I personally use the Osprey Farpoint, but there are many in the category to choose from. Not only is it much lighter than hard sided luggage, but it's typically much more forgiving of dimensional requirements, and can often fit in overhead bins, where hard sided luggage may not be able to (if you're the last person trying to put something in the bin).
And on top of all of that, it's been much more reliable for me - I've had and seen roller luggage fail pretty often - at both the wheels and the handle. Neither of those exists on the bag, which just keeps trucking.
I get that for many people a travel backpack isn't an option. But if it is something that might work for you, I highly recommend it.