Well, if he's dressed as Nightwing, people wont think he's Batman obviously. Theyll know he's not Batman, and that Batman is dead but that this new person is inspired by Batman. To me Bruce never wanted copy-cats. He was willing to let Dent be Gothams hope. Bruce sending Blake to the cave was like "im giving u a choice, if u want this, everythings there".So yeah, basically you're saying what I'm saying : Blake has to be "Batman". He has to be identified as Batman, wear the symbol, use the bat signal, etc. You'd rather have him dress like Nightwing? Yeah. Sure. Why not? As long as people think he's Batman, the symbol is still there.
People think Batman's dead and it's a reason for him not to be Batman? All the opposite. Show up as Batman on your first night out, show them Batman can't be killed and will always be around. That'll scare the **** out of criminals. That will make him "everlasting". The legend who ended Gotham's siege and survived a nuke. Criminals are already packing.
That's what I think, yes. I wouldn't be so affirmative as to what Nolan believes or not, but it seems to me everything in the film builds up towards John Blake taking up the mantle that was handed to him to make Batman eternal.
I clearly see where you're coming from, and I think the way you see it is also has a poetic ring to it, with this "symbol of hope" taking many different forms and identities as it is passed along.
I personally don't think that's what Nolan was implying, but then again, it's just my opinion. We approach it differently, and I think both views are equal.
I'm a big fan of the "Batman is eternal" concept. I don't think the costume has to stay the same. Just the legendary character, that can conquer any odds and last forever, as if there was this Order of Dark Knights watching over Gotham through the ages. The main reason I'd "want" Blake to perpetuate the Batman persona is to show Gotham that nothing will kill him or stop him from protecting them. It sends chills down my spine to imagine a scene where Blake goes out as Batman and is spotted for the first time after the nuke.
t:No Blake parodies so far.

Wait, so people were actually expecting this?![]()

) and Batman made it a point to have him rescue people instead of beating up bad guys. Even in a pinch, Batman/Bruce will choose to rescue people instead of getting the bad guy, as we saw in TDK as well as TDKR. So. Batman is meant to be a symbol of hope, and Bruce probably hopes for Blake to adopt the detective role and helping Gotham that way, more than the "beating up bad guys and making himself vulnerable to violence" role. At the very least, he expects Blake to be better at sticking to his morals instead of going all paranoid cell phone spying on everyone in Gotham. 