Proposed resolution:

Remove the following signature from [meta.type.synop]:

template <std::size_t Len, class... Types> struct aligned_union;

Remove the second row from table 51 in [meta.trans.other], starting with:

template <std::size_t Len,
class... Types>
struct aligned_union;

With the arrival of extended unions (N2544), there is no known use of aligned_union that couldn't be handled by the "extended unions" core-language facility.