To me it is very simple.
Long term, i.e building towards 2019, which combination of halves will perform the best , i.e who will develop to be the best.
First to decide that you need to evaluate do you think the individual player is good enough and will last to 2019?
Genia, Cooper and Foley yes. Phipps I have my doubts.
Lourwen , Lucas, Stirzaker, Gordon could all over take him.
That said you pay the short term pain to develop the combo, I don't care who is better as a combo now and not look towards potential. Otherwise you may be stuck with a less than optimal combination just because time was not put into it.
You should not pick Foley because the half is Phipps etc.
You need to develop the alternatives.
On the other hand if you know Phipps is not long term that you are looking at replacing him as soon as a couple on the horizon improve , then sure play the 10 who works best as a comb right then and there since this is a short term selection anyway.