You should wait for pistons and make an auto cobble gen.
Sounds ambitious.... but a bit overkill maybe?
All cobble generators have the same flaw, they need a person to mine the output, there is no automatic way to break the blocks. Since a piston powered cobble generator can produce cobblestone about as fast as a person using an iron pick can mine it, so, I don't understand why you would ever need 2,500 generators? There will never be 2500 people on the server at the same time. The max limit is 50 slots, and we rarely reach 40 on a good day. I can understand having 2 generators per person, though.... if you had a diamond pick, you might be able to keep up with 2 generators worth of output, max.
So, I can't see ever needing more than 100 generators in theory (50 player slots x 2). In practical terms though, since most people don't need massive amounts of cobble, having more than 10 people at a time wanting to use the facility would be very rare. So, around 20 generators will probably all that will ever be needed.
If I were you, I would make 20 really decently laid out generator stations, with the focus on being able to both mine, collect, store/smelt, and make new picks, all from one spot, at each generator station.
I'm moving out, from that area, as shown in my other thread, to a place in the snow biome nearby, but i like and understand the need to reduce the number of generators, and i shall when i find somewhere interesting to build, I was also thinking of placing a small 6 tree treefarm by each generator along with a chest and crafting table for the creation of picks, the problem with obsidian gens is for the one i have seen, a bucket of lava is needed per obsidan so surely it is just as easy to do it at the lava pools where you get the buckets of lava from.
Actually there is a technique for generating obsidian using redstone which the majority of the community dont use.
Thank you so much! 
