Hi!
I thing for blob it would be enough... In fact I don't know for what would I use small binary field but maybe somebody could need to put there some data and there is no other way than uploading...
I also would think it suffices to upload data to blob fields. Maybe we could put in a configuration directive to enable upload to binary fields disabled by default? So anybody who's willing to clutter his interface with many upload-buttons, he can make it so.
Maybe it would be better to put uploading stuff on separate page and add on tbl_change (and maybe also on display_tbl where [binary] is being shown) only link to that.
I don't like the idea to split up the interface to another part. I find it quite intuitive to have the upload stuff where I want to alter or insert data. Linking to another page is discomforting for me, and maybe also other users.
I think the 'edit' button on display_tbl should be enough to alter the data. Another direct link - if I understand your approach - to upload is in my opinion too cluttering.
$0.02 :)