First, you aren't speaking to Apple here. This is strictly a user-user forum set up to provide technical support. If you want to make the request to Apple then do it via the iPad Feedback Form —
http://www.apple.com/feedback/ipad.html
First, though, you may stop and wonder about how Drag & Drop is
already working in iOS in any number of apps, which, by the way,
does include Safari. It may not work on some particular site that you're interested in, but certainly does in others.