To me, reading the key-value structure of attributes is a little difficult without the common structure of braces. An option is to use object-liter-like notation:

import {foo} from 'module' with {type: 'json'};

Since braces are already used with imports, and they aren't actual expressions, I don't think this would be any more confusing than what we have now. Both uses may look a bit like expressions (destructuring and object-literals respectively) and that's nice to intuitively understand some of the syntax, but they aren't and this is ok because import is special.