I agree that it's not necessarily necessary, especially with a small yard like that. They'll probably be in the run and even if not, I don't think there's too many predators to worry about and what ones there are a secure run and coop will help.
Although I do advocate for getting a dog
I will say though that Belgian Sheepdogs (or Belgian Shepherd, Groenendael variety. For some reason in the U.S. they are separate breeds but in other countries they are one with 4 varieties) are very demanding dogs. You seem to know that already, or at least a little bit, but it is not just the exercise. Some varieties are more or less demanding, like for example the Belgian Malinois is highly demanding, but they are all demanding in their own way. They're very smart dogs and attached to their owners. Even if they weren't energetic and intelligent dogs, they want to be with their owners so I don't think being alone so long would necessarily be fair. Although 6 or even 8 isn't as much as some jobs and could actually probably work out. But do keep in mind that it's more than just exercise for them; they need a lot of training and mental stimulation too.
I don't mean to completely bash it or come off as mean or a know it all or anything, because I definitely don't know that much, just know some people with them,; just concerned for you both cause sometimes smart dogs are too smart for their own good lol
You sound like you've been doing research though and would make a great owner of one on day, if not the first dog
That said though, I know people who do tons and the dog still gets bored, so even if you did everything or left them outside instead of a crate, I think they'd probably get bored being outside all that time and.maybe tear up your yard or find a way out.
But I also don't think that you necessarily have to start with a less demanding dog as a first dog. People like to say that but honestly I think as long as you do all research and fully prepare they would be a fine first dog.
Just maybe not needed as a chicken guardian or to be left outside. Lol
They're also a herding breed so if you did decide on a guard dog, it may be better to get a multi purpose dog like an English Shepherd, or a specific LGD (Great Pyrenees and Anatolians are great, though LGDs can be protective. but then so can shepherds) as they'd probably be happier laying there for hours. My Lab/Pyr mix will gladly sleep on the couch all day but will also gladly go on adventures haha
But again, sorry for the long post or if I sound rude or anything.
If you want I can connect you with some.of the people i know that have the breed