Linkshells are inherently more limited becaase of the membership count.
I'd love to see FC alliances come along, there are a lot of smaller FCs, and medium sized ones who's members have friendships with other players creating a great deal of overlap. FC alliances would allow small/medium Free Companies to join forces in effect making them larger, without sacrificing their individuality.
I'm not sure that this was primarily intended to bridge a small number of large FCs together to work around the membership limits. I think that actually the idea was to allow several small or a few medium sized FCs to ally themselves and work together as one, without sacrificing their individual identity as difference FCs.