Currently, the only way to view people banned from the channel is the channel settings. I think it would be very useful to have some kind of moderator dashboard which displays it as well.

Each entry on the ban list should include: date, current username, mod who performed the action and a space for adding the reason of the ban (editable by the mod and channel editors). It could also be useful if the entry listed up to 5 recent messages by that person posted before getting banned.
The list itself should be searchable by username.
When a user gets unbanned, the entry should stay on the list with some kind of indication that the user is not banned anymore. Additionally, it would be convenient if the unbanning was noted in the entry if the user gets banned again but search feature itself (listing both cases) would be good enough in that situation.

Currently, many channels create lists outside of Twitch to keep track of the bans but with the name change feature being released and no way of checking previous username of the person, it may become more difficult. Ban lists are important to avoid accidental bans and to be able to clear the situation when people ask to be unbanned.