The fact of the matter is that any potential supporters in North Sydney that would be inclined to support Manly as they are would do so already whether or not the Bears juniors are under the Sea Eagles control, and obviously there aren't enough of them willing to do that otherwise we wouldn't be having this discussion.
Having proper engagement from an NRL club goes a long way to getting people interested. It makes a big difference if a kid can come home from school boasting to their parents that they got to meet Tommy Turbo who plays for the Blues and got a footy signed by him. Those moments make their mark on kids. As it is, kids on the North Shore don't get much of that. Manly doesn't do events at carnivals, junior footy games etc as Norths don't want them to.
You allow that to happen and the pendulum begins to swing.
That means that if you are going to attract them then you need to make some changes to make yourselves appealing to them, and two obvious changes that could make a big difference is a home ground in a more central location and a re-branding so the club actually makes an effort to represent the people that they would be claiming to represent.
The home ground is a big issue, but it's a very tough one. There aren't many locations where a stadium is viable on the North Shore or the Northern Beaches. You have North Sydney Oval, which isn't going to be redeveloped into a proper rectangular stadium due to its heritage status, Brookvale Oval and a handful of potential other sites which all have something wrong with them. Chatswood probably doesn't have enough land available to build a decent sized stadium, Rat Park is too far away for most people and so on. Brookvale isn't great, but when you're travelling from the Upper North Shore, the difference in travel time between Brookvale Oval and home and NSO and home is usually a few minutes tops. The big difference is for those on the Lower North Shore, where NSO is minutes away, but then if you live somewhere like Willoughby or Mosman, Brookvale really isn't very far away either. It's not ideal, but there isn't much choice.
A big rebranding isn't necessary. I didn't see a grand rebranding of St George when they took over Illawarra, they added Illawarra to their name and occasionally throw a Steelers tribute jersey on and that's it. And that was a merger. This wouldn't be a merger, it would be Manly handling development of the North Shore. The only rebranding necessary would be adding North Sydney/North Shore to the team's name and logo in some form, otherwise the name and colours would stay the same. You could do a few other minor tweaks, like change the circle logo to a shield design,
ala our 60 year logo, to indicate a new direction, but a major rebranding isn't necessary.
Let's put it this way; if roles were reversed and the Bears were trying to attract people from the Northern Beaches to jump on board, would you make a commitment to them if they had made no concerted effort to make a commitment to you? Of course you wouldn't, but here you are expecting different of them.
I'd probably always be upset over losing the Sea Eagles, but if the Bears were the ones who made it out of the merger, 20 years had passed and it was now quite clear Manly was never coming back to first grade based out of the Northern Beaches, I'd definitely see the writing on the wall. If Norths adopted our territory and our junior districts and added Manly to their name, I'd accept the inevitable. If my kids came home from school or a footy carnival and were stoked that they got to meet Bears players and said they wanted to go see them play etc, I'd take them. There would be others who wouldn't, I assume, but once enough time had passed, it would just be a natural thing that they control the Northern Beaches.
As I said though, the Bears making such a move wouldn't be about people like me. If they managed to make a supporter out of me, they'd be very happy, but their moves in the region would be about getting local kids on board, engaged with the team and becoming longterm fans, who would pass that support onto their kids and so on.