Thanks for your replies
Just to clarify a couple things:
Yes there is a router at the beginning, just easier to show it as I did.
The wireless link I show, isn't just a usb wireless adapter, im using a pair of Open Mesh OM2P units, which, when setup correctly, can be the equivalent of a wired network.
There is a very good through put on the wireless link, as I hve had a gaming PC on the other end (wireless end) and it performs perfectly with my 52mb fibre internet.
As it is FTTH i'm getting around 5mb/sec download.
So I think the internal network is quite good with regards to internal speed etc.
I basically want, all PCs, phones, tablets etc to go via the server before hitting the internet.
At this stage I dont have much of an idea why, but I like to experiment with things, mainly to see if I can do it, but I just like getting things up and running.
So the answer to "why" i dont really know, just want to.