I was actually under the impression a while ago that the limit numbers for FC and LS were reversed. Reasoning (at the time) was to have smaller groups for the Global summoning system as well as housing, PvP and world standing to generate more competition for these things.
Global summoning (which we really need more updates on) was going to be like the Odin and Bahamut FATE wherein they are rare events. Then a Free Company that defeated it will get the ability to summon it once for a massively powerful move. This would be (i'm guessing here) a claim type system. It was said to be something that everyone in the server world will know when it has been defeated then used so others will know it is available in the world again for defeat and summoning.
PvP was said to have Free Company Rankings involved in the gear rewards as well as ladder rankings. (again, it may be very outdated or incorrect information.) I know Grand Companies also affect this.
There is also the ranking system with the different Grand companies in the Free Company system as well as the Free Company rank itself that will have a reward system that gets expanded upon. With smaller numbers this will allow a more level playing field of competition for all Free Companies to be able to compete. (this is basing off of the 128 number I thought was going to be for the FC limit.) It would be easier to have Free Companies that are not able to attract or dont want to attract large numbers of people (I remember seeing in this thread the "Quality > Quantity" argument, that fits our FC motto) Then the larger LS number would be a good way to link the FC's together for major events and such.
i could be wrong and I'm not saying I agree with that but just wanted to mention some reasons I remember hearing to justify the smaller numbers. I kind of think the LS number is the one that need two more 0's on the end to link the FC's together.
Just my 2 gil