I think, to answer the info you want:
Higher spoke count for more 'strength' + if well built will stay true (straight) easier.
Shallower rim - easier to spin up /slow down due to lower weight at the rim.
Alu, because rust won't be an issue and carbon is more prone to damage from knocks etc.
Hand build you already have some solid suggestions. Off the peg Halo aerorage or aero track are both pretty bomb proof.
If I remember rightly, aero rage are wider, so better for a 28c tyre- which if riding all day will aid in comfort.