Pre-fill Taxonomy on add content page (I'm already using prepopulate)

I want to create a button on a Taxonomy page that allows a user to add a specific type of content to that taxonomy page.

A simple link to the Add [Content] page is fine, but I would like for it to pre-fill that Taxonomy for them and not allow them to change it. I found the Prepopulate page, but since this is going to be on every Taxonomy page it has to send the specific taxonomy on the fly. I've figured this out as well, but the way the Add content page works is it is a drop down menu.

- Please choose -
Item 1
Item 2
Item 3

The way Prepopulate works on a drop down is it takes the value number and not the actual name. The problem is I can populate with the actual name and not the value number. Even if I somehow did figure out the value of a drop down if a new taxonomy is added it could mess things up. I would like this automated as much as possible as there will be hundreds of Taxonomies so I don't want to have to manually do this.

Too make a long story short.

Is it possible to change the way the Taxonomy list is displayed? I know when you go into tagging it makes a box. I guess I could hide the box with the pre-filled content so the user doesn't see it. But my fear is they'll somehow get to it and add extra Taxonomy that I don't want added as I don't want this to be free-tagging. If I could even hack that specific page to change the input that would be great.

Any suggestions?

Just some more background I'm using Panels and Views to override the Taxonomy page. I was going to add a link to add content with a simple Add Content