Reasons why Nappa should still be around:
* He'd be able to be a good guy. Nappa was evil like any Saiyan, but it mainly seems to be part of his culture than his own decision. He actually cared about the Saiyans, considering he wanted to bring Raditz back. If Vegeta can find redemption, Nappa should
* He should logically be back. Everyone killed by Frieza and his men was wished back. Vegeta was one of Frieza's men. Yes, I know it wasn't by choice, but if something as loose as "dying of heartbreak because of Frieza" counts, I think Nappa should've counted...wait a minute, it's actually "Everyone on Namek." Nevermind. Which is dumb, because they could've brought back Yamcha and Tien immediately if they didn't specify Namek
* He adds something to the series, and is generally an understated character. Nappa is the only Saiyan left who was an adult when his world was destroyed, and grew up before Frieza even met the Saiyans. He's a first-hand experience into their society, and would certainly help with Saiyan knowledge