I have a old Victorian house in Melbourne I dont want to touch the current building and considering building a second story on top of my lounge room

The room I want to go on top of is 7 m long 4 m wide

Does anyone see a problem of me building around the house using the following stump method

The only issues I can see is

A The height is 4 m
B How would I brace it

http://surefootfootings.com.au/gallery/