That could be interesting if you could only use lines from a book or a play. You could maybe pull a book out everytime you want to speak just character fluff.
Mimicking your party members' actions could be an interesting way to roleplay the bard's Jack of All Trades.
I used a kenku bard as an NPC in my last campaign. It was great to have him just perform covers at the local inn, and to impersonate party members to eachother :D