Introduce Personnel Transportation Game Mechanic

Introduce a new factor in productivity/happiness, the time/distance/transportation-options between home and work. It would create incentive to build multiple cities or fast rails to keep the score/bonus high. Buses and Trains with stops/stations would allow more remote areas to still score well but up to a point you would need to build a new city nearby if you're on the other side of the island.

You beat me too it. There need to happiness zones based on proximity to housing. Closest get a nice bonus. Next zone has no bonus or drawback. Past that is an increasing drawback. Buildings draw workers based on priority and proximity to housing or passenger stops. Passenger routes can be though of as pipes for virutal people... more actively running transport equals more capacity to the station. Stations also have a capacity, just like storages. Better transport and stations give a more happiness boost, with more options available with research. Mini-bus/bus/coach/passenger trains for vehicles. Bus stop/bus station/large station (mixed bus/train) for passenger stops.
Hmmm... helicopters, anyone! Airliners!