Removing or changing the Edit/Del links in Activity History

First off I am on Enterprise Edition

My Challenge is I have not been able to find a solution to this question. I want to remove the edit/ del links from the Activity history on the Accounts object

http://screencast.com/t/1dkRRkeX

There are no user or profile permissions that I can find that can achieve this.

This is very important has we recycle leads based on no activity for the last 30 days and we found an employee deleting others tasks to make the activiy history look like it was more then 30 days old

I still want read access to the tasks for all users but no option to delete them .

I tried this permission

http://screencast.com/t/zh0etRe2

That removes the buttons however they can not create tasks then so Email to salesforce or logging tasks no longer works and that is no good

Does anyone have any suggestions on how to solve this issue?