aluminium frame with min 10mm toughened glass

example: winding staircase, source internet Little modification need to be done for entrance lobby opening, where you could accommodate a shoe rack and the complementary vertical wall can act as a amazing entrance decor wall wall in Kerala style heavy color play or texture/wall cladding with brass mural.. by doing this you get space to mount TV unit and a good space for sofa arrangement (make sure sofas are light as the space is less to accommodate baggy sofas), staircase can be made in the shape shown in sketch plan, with marble finish on the foot steps (or as per interiors), space in the bottom of staircase next to master bedroom wall can be utilized for chest of drawers or a tall furniture, make sure the staircase bottom part to be casted smooth in finish.

It is a very easy fix. You may get a slope made in sheets/metal/ red sand tiles etc over the windows and the French window. Although the French window is close to neighbours home and wouldn't be exposed to heavy rains. To answer your query, sometimes people do use these window ledges for AC compressor. Did the architect plan required them to make it in H shape?

Mukti, From what you described, it seems you need a water softener than a hydrophobic coating. Salt based softeners are good for these issues.