Well, I know these little garden tractors can be used for variety of chores. I have seen an ad for the Johnny Bucket, but that is about it. I don't know anyone who has one or have any knowledge of how convenient they are to use. I have, however, spoken with a company who builds a custom front end loader for the 3000 Series Cubs. I didn't plan on buying one, he just mentioned to me that they build them. With the hydraulics available, I suppose there are many possibilities. I would caution against overloading the tractor. Yes, it does have a cast iron front axle etc, but even at 800+ pounds (minus the deck) it is still fairly lightweight for some chores. After I get mine out in the grass and run it for several hundred hours, I will have a better idea of what it is capable of doing. It is still winter here yet in North Dakota so for the time being it just sits in the garage.
As far as the loader work is concerned, I have a Ford utility gas tractor that I use. It is large (about 48 HP) and probably too awkward to use inside a barn, but outdoors loading dirt it is hard to beat. It is old and doesn't have FWD, but it doesn't seem to need it. The new compact tractors are no doubt much more handy to use, but then, they cost over $10k and I paid less than $3K for my tractor with the loader. It has a 3 point and PTO which is somewhat unusual for a utility/industrial tractor. It has fluid in the tires, but I don't have any chains for it, so moving snow is impossible. It just sits and spins.
If your goat barn is somewhat cramped...pens etc...you might consider a skid steer type loader. I have used them before and when it comes to loader work, they beat about everything. There are alot of good used ones around also at similiar prices to a loader tractor. I would recommend one with liquid cooling rather than air cooled (the older ones). My uncle works for Melro, so the Bobcat type skid steers are my preference.
