You can have clients access the portal, and if you give them technical rights, they can see contacts, documents, domains, certificates. They can't see licences or assets.
Fully appreciate some companies wouldn't want clients to see it (so should be a setting), but for some clients, if they could see which assets they have and who they're assigned to, it would assist (since we're recording them anyway). Perhaps also the current location and physical location (we use these where a computer isn't specifically assigned to a contact, like a PC on a counter, in a warehouse etc).
If it was to be useful for an asset summary, possibly the purchase date? Obviously limiting visibility of who the supplier was etc etc.