I absolutely agree. Dick with a sidekick (or junior partner) is always good fun. He had the best dynamic with Damien, and his brotherly relationship with Tim back in the day always felt genuine to me. Not to mention all the great moments we've gotten from Nightwing training younger Titans. So hell yes, Dick getting a sidekick is something I support.
Additionally, I think that having a legacy/partner/sidekick is one of the requirements for a property/character hitting the A-list, and I very much want to see Nightwing break through that glass ceiling.
As for who this sidekick could be? Whoever the best writer has the best idea for.
Now, I myself would like to see Bette return to the Flamebird identity and become Dick's sidekick (but not love interest). I think it'd make for some good tension with Kate, and Bette and Dick have a solid, enjoyable dynamic. There's precedence for "Nightwing and Flamebird" and these days Bette is written as being both younger and less experienced/skilled than Nightwing, so I don't see the sidekick position being beneath her.
Jon Kent....I'd like to see him meet and build a relationship with "uncle" Dick but I don't need to see him slide so deeply into the Bat-clan that he becomes Dick's sidekick. His friendship with Damien and the occasional team-up with Nightwing (or Tim or whoever) is enough. But I do want to see Dick have more of a relationship with Clark and Clark's family. Dick and Clark were close once, and I miss that relationship. I think Clark, Dick, and Jon together for an adventure would be amazing.
But you know who's half Kryptonian and needs a new name and role in the DCU? Conner Kent. He's coming back in Bendis' Young Justice, with the 90's costume even, but I dunno if he's gonna be calling himself Superboy now, nor what his role (if any) is going to be within the Superman family. But I really liked the few times Conner and Dick hung out (there was one issue during Infinite Crisis where they travel together and I thought it showed potential for the duo). So if he's going to distance himself from the Kents, well, he does have an uncle he barely knows out around Gotham. If ya'll couldn't tell, I'm a big fan of Nightwing hanging out with the Super-family more often just on principal.
I'd rather not see a character like Carrie Kelly introduced into the main DCU just to be completely changed around, stripped of the Robin mantle and turned into Dick's sidekick instead of Old Man Bruce's. It just seems pointless. At that point, the only thing she'd have in common with the original is the name (and presumably red hair).
Spoiler, Signal, Cass Cain, and Tim all seem like viable options. They're Bats without a home, but that sort of feels like throwing them into Nightwing's house because no one else knows what to do with them. Still, I love Tim (or rather, what Tim used to be) and I like Cass a whole hell of a lot, so I wouldn't argue if this happened.
Someone new could be good, honestly. Custom made character designed to fit the role.....it's not the worst direction to go, though people will complain about a new character coming out when so many other Bats are in limbo or barely getting used.