Pierre Charles L'Enfant's architectural philosophy was such that, a building should not be taller than the width of the street it stands by. If so, I think the quakes will have less likelihood of toppling the structures onto other buildings and will also allow enough daylight to spill into the streets. I wholeheartedly agree that buildings in the UNESCO heritage sites should reflect the traditional Newari architecture while the underlying structural soundness is re-enforced with the latest building technology. The street hawks and the loiterers should NOT be allowed to tamper with the ancient structures so as to reduce burdening their fragile life. At least locally, new building-height restrictions should be enforced so that the historical buildings dominate the skyline in the vicinity. The compounds within each UNESCO world heritage site can be ticketed  at least nominally to prevent overcrowding and to self-generate maintenance fund. The Nepali government could budget a fund to fence these architectural jewels once totally restored.