Is it reasonable to plan 8 days in Ireland and then plan 8 days the follow day in Scotland? How do I go about planning and making the proper flight and other travel via bus or ferry?
With such a short time, fly between the two.
You will just scratch the surface of both places. To advise further, we'll need more info about your goals. Do you like cities or countryside? Do you want to immerse yourself in one or two locations per country or see a greater variety of destinations? Are you open to taking organized tours--for example, a day's bus tour outside a city?