I had some more ideas (to get to edit the extension list in the settings page for example)
but it's mroe than average work so I thought to aks you what to do first.
Here is what I had:
Add some random thing that is not an extension (so it will not get blocked) into the array. Somethin glike "LASTLISTENTRY"
Then, on the settings page, do a foreach() on the array of not-allowed list, and filter out the last one.
Make a delete buttion per word, and do a replace function-ish to remove it from the array.
If one wants to add a word, replace , "LASTLISTENTRY") with ,".NEWEXT", "LASTLiSTENTRY")
that way it might be possible, but to me it seems too much work for something that can be editied by simply opening up xedit.php anyway..