You'll only get ex-north fans, if you add the name "North" to Sydney Roosters, and you might have a better following.
Although i know that the North Sydney Club would prefer that the "Bears" would be their prime name even if a new venture in CC/Perth/wherever was enabled for them to re-enter the top grade as stand alone, but for me, a proper merger of the two, would generate tons of support
With North Sydney Roosters (or North East Roosters?), we would finally have foundation clubs Norths, Souths, Easts, Wests and Balmain all represented in the NRL in some form or other.
THAT would be a huge boost to the NRL in Sydney, IMO.
In this scenario, Roosters hold all the cards. A wealthy club with a certain long term future in the NRL.
The Roosters moved away from the Easts branding long ago, against the wishes of their own fans, for the broader Sydney header. There are undoubtedly sponsorship, national and international image benefits to the Sydney branding - the club won't regionalise itself again.
Bears, as a NSW Cup club with almost no serious chance of an NRL revival, can only offer junior territory, which doesn't actually have that much value. Roosters are the most successful NRL era club with a small junior territory. 2 and 3 are Melbourne and Brisbane, neither of which have junior districts in the same sense that Sydney clubs do.
There's no value in a name change - North Shore pretty comfortably fits in the Sydney banner obviously, and the area shares a pretty similar demographic to the Roosters traditional region.
And Bears don't hold enough cards for the Roosters to offer changing their first grade jersey, colours, name, or logo in any "merger". Bears don't hold anything that Roosters couldn't just takeover by applying to the NRL, if the will was there to so. But it would be better for all if it was a partnership rather than a takeover.
I believe Roosters and Bears should partner in football operations at every level from NSW Cup downwards, and lock in in long term.
What Roosters could potentially offer:
a guaranteed long term position of strength for the Bears in the NSW Cup by being linked to the most successful NRL club.
a guaranteed long term pathway for North shore juniors to the NRL.
increased growth at grassroots level with north shore schools and junior clubs being linked to the Roosters NRL club.
increased fan support for Rugby League and the Bears in the north shore by Roosters making a deliberate long term joint-promotional effort to reclaim the "lost" fans
There's no reason, a generation later, that the north shore should remain lost to Rugby League.