I would say you would replace the poison entry with acid. The planetar gains no bonuses against poison. Therefore, the planetar infused gains acid resistance equal to half her infused level at 2nd level and immunity to cold and petrification at 10th level.
Try emailing this to Paizo. Ten-to-one it'll get printed, along with an answer, in a near-future issue (unless someone else has already asked them this).
Great minds think alike. I was doing that while you were typing the reply. If only I had thought of that sooner. I was too busy looking for an answer here and on WOTC. Well thatand it's almost 2 am here but too warm for me to sleep with my wife.