Songstress ;]

Pretty much counts too (as you're forced to transform into it in the second battle).

Don't forget to spam songs! having a +10 in that certain buff can reallllllly help in terms of buffing up damage.

As for dances... maybe only to really level up (Pilfer EXP works a sort of charm too >_>)...

I reccomend using three gunners later on as they can get some NASTY damage with the EXP Shot or whatever it's called...

And yeah, you're all set :3

Edit: I did a similar challenge to this (Cept I used acc and ggs >_>)... It allowed me to appreciate the Gunner other than for spamming Trigger Happy and well, My most recent play through had me constantly switching to a Songstress in the Via-Infinito, on the later floors :]