A great business differentiator, and something that could be much easier to execute at Apple (due to them controlling the whole stack) would be to create a full

A great business differentiator, and something that could be much easier to execute at Apple (due to them controlling the whole stack) would be to create a fully trusted platform. That is, design all hardware and software in-house, and use formal methods (theorem proving, program analysis and model checking) to verify everything. Furthermore, adopt a Qubes-like architecture where external untrusted applications can be run in an isolated way.