Q2. If a new feature requires a major investment in terms of new
architectural infrastructure which is going to take multiple sprints
to develop (it's 3 months work), what do you deliver as working,
tested code at the end of an sprint? If you spend lots of time
developing unit tests for this, they are pretty much useless later in
the process once more of the design has been implemented and are
therefore seen as wasted effort.

Q3. Does anyone know of a real world example that is well documented
somewhere which shows the power of Agile in a complex embedded
development environment (not applications)?

Both of the above are being given as objections to us adopting Scrum
and I'd like some help removing these blockages.