Hi. Actually if user want customize his affiliate link have to ask the referral word and admin must create that link in the website to avoid 404 error and after tell him. This system is not good and too much complicated. I suggest you to create the affiliate link with referral word similar to the automatic url generated (http://www.yourdomain.com/?referral word). In this way user can choose the referral word on his dashboard directly, admin doesn't have to create a link for that (imagine how many links admin must create if every affiliate user ask it) and the component validate the new affiliate link only if no one already choose that referral word.
I hope you can think on it to improve a nice feature in good way.

Best regards