Yes, I think they could. They have the best engineers in the world and incredible amounts of money. The regularly invent new manufacturing techniques to enable their new designs. They often invest heavily in their suppliers to enable them to make the parts they need.

If Apple wanted to they could make an iPhone that people love and has all the features they want and be much easier to repair then the current version.

Apple tried to make the MacBook Pro just a few millimeters thinner and gave us the disastrous, almost-universally-loathed butterfly keyboard. I feel like your view that Apple engineers have massive design margins they are choosing not to exploit is just not real.

Maybe your view that a massive design margins are needed is not real.

Literally the choice of glue can make a huge difference for ease of repair with no impact on the design.