Agreed, a simple majority for emergency powers is ridiculous. I'd go with at least a 4/5 threshold myself. More than that, any invocation of emergency powers should force a public confidence vote for every elected official when the (strictly limited & non-extensible) duration of the emergency powers expires, where any incumbent who can't achieve at least a simple majority of support following their handling of the emergency is barred from political office for life. That ought to make them think twice about whether declaring an emergency is really worthwhile.