A problem and sugguestion on watermark

I did select applying watermark on Full size or Resized image when adding item,and then it seems working fine.However,If I rebuild resized images and thumbnails,the watermark on resized images will disappear but remain on the full size images. Did I do something wrong on settings?

And also,I found that it's painful to update watermark on large number of photos .So,is it possible to add a "batch-applying" function of watermark to make the updating job easier?

Thanks you :D