The only way to combine AmEx and Chase points is to transfer to a shared airline partner (such as Singapore, or British Airways to redeem on Cathay Pacific). The bigger issue, though, is that you are in no way guaranteed to find saver space, especially if you can't be super flexible on your travel dates/airports. I'd focus on locating the saver space first. If getting two saver awards requires buying an additional 15k miles, that's still a very reasonable redemption.