There is no way for a form to check if a person has applied for that tracker before.
There is no way for a form to check if someone has used someone elses proof.
There is no way for a form to check other threads, so it cant prevent you applying in another GA.
There is no facility available on the forum to allow what you are asking for Hearts, in fact I don't think there is one available full stop. If we were even to consider going down the template route it would be a set reply template that everyone would have to use, there would be no facility to edit/personalise it for specific requirements. I know for a fact that permission would NOT be given for everyone to set their own template via the forms mod as it would mean we would have - 130,182 different forms (1 per member).
Add to all that, the fact that you need a way in which to force people to use your template (links will not suffice as people wont use them), the only way to do that is to code the reply button to the specific template set by yourselves which is impossible as you would need to create a new button for each thread created and then code said button to your individual reply templates, meaning you would need root access to the database and that is never going to happen.
The suggestion in its basic form is good, but the reality of it all and what you are asking for can not be done.