There's no reason such a laptop can't be repairable. Sure, it may be harder to do, but that's the tradeoff you choose when buying such a device.

The main obstacles to repairability in such devices are intentional: part serialization, lack of documentation, and so on. Those don't help making the device any more compact or easier to manufacture, it's pure greed.

Address those problems and you can happily have your ultra-slim, tightly integrated laptop. It may be slightly less repairable, but as long as repair isn't intentionally being prevented, life will find a way.