Ultimately the only thing anyone can do when running into a restricted username is to choose another I'm afraid. The moderators on the forums do not set the rules for usernames nor do we upkeep the list of restrictions.
Support can take a look at these cases but we can't say if they can actually help or not, depending on what it takes to rewrite rules, get permissions to do so, etc. It's not so cut and dried but if anyone could help it would be Support.
If you would like to reach Support and ask if they could help you can do so here:
If you would like to submit a Support Ticket for help you can do so here:
https://support.ubi.com
You can also reach out to our Facebook and Twitter Support pages here:
https://www.facebook.com/UbisoftSupport/
https://twitter.com/UbisoftSupport