i'd say you nailed it. he fits his character SO perfectly

I think his character fits Sanji more. :P
This may sound weird, but...
I had hoped Usopp's player would be more likeable and smart. I like Usopp and think he deserves more credit.

It's amazing how quickly you can learn to be good at something when you've got the right motivation.

No, would'nt be interesting if he played Sanji. also, i'm pretty sure Sanji would have to be played by a munchkin who have experience in tabletop, like for Luffy and Zoro.
while someone who is'nt particularly used to RP and don't know how to minmax, but is quite smart, would fit for Ussop (now let's just see if Phil is smart, which he might very well be).