no worries Kiwi, you can indeed use a bt016 at the front and a "harder" tyre at the rear i.e. BT023. Many people use this combination when the weather gets colder here in Europe i.e. soft @ front and hard @ rear (some of my friends even use a rain tyre at the front...true!) they got the feeling of a better feedback given the poor riding conditions.
However as it is mainly the case when regarding tyres, we will all have a different opinion so best thing to do is to try it and if you are not happy, put the complete set of bt023. But again, there is nothing wrong nor dangerous using different type of tyres on a same bike, as long as you respect the tyre' size and dimensions for the bike.