I don't think there should be any other functionality to families other than the ability to chat. I originally suggested this as a way to replace social guilds, and I think the new guild system they're working on will have a lot to offer for guilds that actually care about gameplay.
Graal is a very casual and social game, so I wouldn't be surprised if the majority of guilds only exist for the chat experience.

I don't see why not, the only benefit you get from recruiting a ton of people is a ton of spam. I guess it could benefit players during holiday events, like recruiting a huge number of players to a family during Easter or Christmas for egg hunting or G4G. I don't really know if that's an actual problem though.

I wouldn't mind something like that, my only concerns against it are that it's probably more RPGish than the iClassic niche of players are used to and younger players may have difficulty understanding how it works.

I do think imposing a limit on how frequently you can join or leave a family would be cool, just to give them some sort of value. Maybe not though, since the rationale behind this suggestion is to kinda dodge a limitation on guild members...

I'm sure they have interesting things to add to guild houses once they finish the guild system update, it will take a lot of time.