Cost for a two-storey entrance addition

We live in a 1500 sq ft Cape Cod style home in Ottawa South and would like to add an office on the second floor by lifting the roof between the two existing dormers (access to the room would be from the Mater Bedroom.

We are looking at two possibilities for the first floor:

1. Leave the first floor open and just have a covered porch

2. Enclose the first floor to increase living space in the house

What would be the ballpark cost for each option?

Included photos:

1. The concept we are aiming for (just much simpler design)

2. Our house

3. Master bedroom (on the left when looking at the house)

4. Bedroom (on the right when looking at the house)

Thank you,

Julie