Unfortunately you can not import more than one web address of the same type at a time. The easiest solution I can think of is to rename the Blog link type. You can do this by following the instructions in the change field labels tutorial. The downside, it will be a bit confusing when manually adding websites because two will show in the list and I not 100% sure how that would affect the import/export.
NOt the best answer, but I hope it helps!