Clients would have to be altered. Every room in Ipoker has the same client, although they have different skins so the houses are well identified.
It's still different rooms on the same network, so they only had to unite to create the network and the new client.
This looks like a good idea but there may be a few problems. Wouldn't this need each site to trust the network maintaining the games? That would have to be very well verified to make sure no scams go on. And if a flaw in the software is found it will affect everyone connected. Then, many new gambling sites turn out to be scams and being associated with one could kill the deal. And also some larger sites may not want to do this to limit how many players they would lose to smaller sites. Smaller sites may not want to do this to avoid having to rewrite code that they just bought from someone else.
I don't know how Ipoker does it, but I can't really see a problem here for anyone. I think the Ipoker network was probably created to solve exactly the problem of a lot of poker houses not having enough players to compete with bit networks like pokerstars, fultilt, etc. I mean btc poker is nothing compare to any of those networks, so the "greedy" way of thinking will do nothing for them. None of the btc poker rooms is a big room, they are all small and can't really compete with Ipoker, pokerstars etc, because of that, so they all have to win if they keep they accounts separate, and just unite their poker networks.
There shouldn't be a trust issue because they will all have something to win because they would just become more attractive to poker players.
I have no idea how the rake works etc in Ipoker, but I'm sure they could just copy the model. I don't see any room complaining about being in the poker network, so I'm sure it works.
Not saying it can't work or that it isn't a good idea. But you didn't really answer what I said. And you keep comparing large and well established sites with smaller btc poker sites. What is possible for one isn't necessarily possible for the other. Like I said smaller sites may not have the money to rewrite their code. And having more people for their players to play against may be too small a reward for now. As for trust, that's not what I meant. I meant all the sites will need to trust the ones providing the rooms and running the games, not each other. That can create other problems, like scams coming from the providers. Or bugs in the code that could affect everyone, and hit small sites much harder. I guess there are ways to avoid these but that takes time and money. And btc poker sites may not be interested in that commitment for now.
Yes the code would have to be rewritten, or a new service would have to be created (one that would offer the new network and the "skins"). If they afford to have one client and be in one network I see not problem to change that client and network for the new client (skin) and be on the new network (the shared one).
As for trust I can't answer it. I'm not providing a service, and if someone would offer something like this I could not speak for them either. Maybe it should be "easier" since now you could point out one company that was providing the network and the client, but trust can always be broken and scams can always happen anywhere, so I can't answer that.