1. Top floor have less problem to deal with then lower floors, leaking roof is easier to settle then annoying upstairs neighbour jamban leaking

2. No worries about water pressure, booster pump is cheap and efficient, if required

3. NO worries about heat, you can always put in plaster ceiling and rockwool for insulation, can settle

4. What I wouldnt do is have the water tank DIRECTLY above the unit.... risk of leakage is amplified, disturbances, and a super duper heavy thing right above me, i dont liek it