Luigi: No, but a new game+ sort of thing like in SMG where you play as Luigi would be kinda cool. Yoshi: A Yoshi partner would be ok with me. There would need to be variation in how the Yoshis look though.
I would say no to both simply because one of the big charmers in the Paper Mario series (excluding Super Paper Mario... Bad game...) is getting a wide variety of partners and not focusing on the same old same old. --- Did you know that 40% of all facts are made up on the spot?
Luigi- I'm all for adding new partners, as long as adding him would not take away another partner. If possible, I would like a unique moveset which makes him very different from Mario...so it's not like having two Mario in the same battle. I like having new party members, but I don't think it would hurt to have Luigi here, even if he's been playable in another Mario game. There is nothing wrong with Luigi being a helper, though I might say differently if he had been playable in Paper Mario 1&2 and actually used as a partner, as I wouldn't want Luigi to be reused.
Yoshi- Been done in Paper Mario 2... a baby yoshi was fun when it was a kid, but one could be way more helpful as an adult Yoshi, even if it does sacrifice cuteness in the process. .-.
But he always served as amazing comic relief in the original PMs. You cant force Luigi out of that role! And Yoshi has been covered as a partner and an area (remember?) --- Mega Man Legends 3, proof that anything that ends in 3 is now eligible to be made on the 3DS. Think about it, it's true!
Luigi: Not a partner, why not an alternate main hero? You can switch between the two, they share the same EXP but carry some different fighting styles and have different reactions to various bosses (Even the ability to skip one or two if you have the right bro.)
Yoshi: Yes, definitely. --- If are a JESUS FREAK and are 100% proud put this as your sig. Favorite Video Game Characters: Mario, Sonic, Kirby and Yoshi.
Yoshi yes. Luigi no, you're already partners with him in the other RPGs. Paper Mario should keep it's tradition of using different Mushroom World species as his partners. --- My signature is two lines long.