Managing User Entitlements

We had hoped to use ServiceDesk Plus to manage our user entitlements. We created a great form so new user requests could be submitted to our ticketing system but then could not find an easy way to keep track of all the services and accounts which are assigned to each user.

Using the "User - Additional Fields" options seemed like it would offer us the functionality we needed but we realized that "Checkbox" is not an option, so our plan to list entitlements on each user's profile with checkboxes which can be ticked on or off when entitlements are assigned, would not work.

Has anyone else attempted user entitlement management using ServiceDesk Plus? How was this implemented?

Thanks.