What airline(s) does he actually fly most on? Many of them (including United) are requiring a minimum number of segments (and maybe miles) on their own metal to qualify for status. So if he only flies EVA, then he might not get status on UA even if he credits the miles there. US is going to be switching from Star Alliance to One World as part of the merger with AA, so that's probably not a good idea if he's a Star Alliance flyer.