* Have pages listing available links go/hr could take you to the HR homepage, but go/hr/_list would link everything that exists under go/hr like go/hr/holidays or go/hr/stockawards.
* Give users a personal links page with personal and private links. Allow the company to display custom news/content on this in a tasteful way. Internal comms want to get their content to users.
* Let users bookmark links from the _list pages I mentioned.
* If a user links another link shortener, or a page that has a redirect, either - remove those intermediate redirects, or flag it to the admin.
* Add some sort of safe site checking to "protect IT from the risks of public link shortening services." Not sure if you can reuse an online database for this.
* Provide RSS feeds of top links etc to import into the company's portal.
* Resolve page titles correctly. If someone pastes the link into a tool that looks up the go link for a preview, ensure you return useful metadata. This is a common problem now because companies have some stuff on-prem (their documents and tools) but are using a cloud chat tool. If you can work out a way to know that particular tools are scraping your link then you might be able to give a better experience.