Ч177
ЧТО БЫ (Б)...
coll (modal Particle
Invar(used in exclamations to express the wish that s.o. do sth. or that sth. happen, express frustration that s.o. did not do sth. or that sth. did not happen etc) it would be (or would have been) good if
why don't...
why not...it would be (might be, would have been
etc) nice if...(in limited contexts) if only... Что бы тебе помолчать. Why don't you keep quiet.