Personally, rather than thinner/lighter I'd pay for it to be a bit bigger but capable of letting me open it up and replace RAM and the SSD as was possible up to the 2013 ones.
The resell market is good enough that you can sell your laptop and buy one with the upgrades you want for around the price the upgrade would have cost.
That's a workaround, not a solution. Not being able to replace memory is absurd. But being able to replace a hard drive (the part most likely to fail) is just evil.
