YMB, because it's a coalition surely does not prevent the whole cabinet...ie the senior members of both parties...sitting down to consider and discuss the ideas that both may be coming up with. Having done that, they might put feelers out around their parties in Parliament to see what reaction emerged. If the reaction was vehemently anti - as we saw with regard to Lords reform a week or two ago - they could either scrap or modify them without the press and society as a whole knowing anything much about it.
Instead, they dream up nonsense after nonsense, publicise them and tell us they're their latest policies only to have them thrown back in their faces...which is no more than they deserve.
Is it your case that the pasty tax, the caravan tax and the granny tax were actually LibDem ideas and the Chancellor just felt he had no choice but to appease them and include them in his disastrous budget?
Instead of blaming the LibDems for existing, do try to grasp the fact that, but for their presence, the Tories would have no say whatsoever in ANY policies, since they would not even be in government at all!