The NRL should really step in over this. At Old Trafford, Fenway Park and the San Siro; Monolithic venues that sell out years in advance, there is still a concession for a small percentage of away supporters. Regardless of the popularity of a team in sport you have to make concessions for the visiting team, and that includes supporters. Its only fair. "Locking them out" is an unsporting act and not within the spirit of any sport or organisation.
The Tigers cant have everything. They cant merge and essentially double their support base, have huge membership numbers and then play fixtures against cross town rivals at venues that are not large enough. They may even shoot themselves in the foot here and the NRL may baulk at giving them Sunday afternoon fixtures there against Sydney teams if there is enough stink kicked up.
The other thing that is complete Bullshit is that Leichhardt holds 18k. As it stands the Tigers have 10k members. So if they have a members only event the joint will only be half full.