Turns out it really doesn't make too much of a difference versus what FileMaker Inc has already done. The amount of traffic WebDirect is passing to/from the client is fairly small and already compressed and optimized. Also, you can't really control how WebDirect is delivering content to the network layer through the application layer anyways (since that's compiled into the WPE), but it's already optimized for WebSockets, so there really isn't a need.
I believe a lot of the 25% net performance gain from FMS13 to 14 was a result of switching from ice.push long-poling to using websockets.
A fascinating read on something like this was someone that tested 10 million concurrent websocket connections on a single server.
Stuff like that is beyond the scope of what you'd ever need for WebDirect.
Your best net gains for WebDirect will come from hardware increases, and file optimization. Additionally, you will probably receive a better gain from upgrading your ISP for a faster upload, then you would from months of trying to tinker with WD. WebDirect and FMS itself aren't really all that tunable, and the WPE is fairly closed off to tinkering.