Controlling In-Shack External Hardware via the Flex-6000 and SmartSDR (even if an add-in module) could be highly desirable.
Would seem an opportunity to push some of the core of what is another layer in "parallel programs" like DDUTIL into the SmartSDR software.
Would simplify LAN and later WAN control by putting all-in-one, including better building a "connection impaired/lost" set of rules for a shack's hardware.
I've found old-school RS-232 is slightly easier to deal with for remotes than USB. Don't worry if you need to add a small distribution Ethernet switch next to your radio. I have four switch hops and under 1ms of round trip latency.
But given that the on-wire protocol is public, I think the long term answer for controlling peripheral equipment is a dedicated network-attached box. It could connect to the radio and listen for band changes, tune requests, or whatever and provide the data in whatever format you want to control peripherals.
How cool would that be, right?
Use something like a PI2 with like 3 dozen digital I/O lines, and you have a lot of control possibilities.
I'm hoping to prototype something like this with Windows 10 on the PI2.
Just starting to work with a 4o3a Station Genius XXL and expecting the Antenna (Switch) Geniuses to arrive in the next 2-3 weeks, a combination that will add a fair bit of what I was envisioning.
May add the Rotator Genius, which pretty much leaves just the Amp, Antenna Tuner and SWR/Watt Meter to get working remotely. (Alpha 95, Palstar HF-Auto and Array Solutions PowerMaster at the home QTH. Expert Amp, Palstar/Kessler HF-Auto and a TBD at the weekend QTH. - so all should be fairly easy to do.)