Equipment manufactures like to make a loader only fit a few models then change the loader design. This makes replacing the complete loader after a catastrophic failure difficult. Buckets are easy to change out and not terribly priced. However its different for loaders.
You can't with a normal backhoe. The snow wedges in the front and rolls off on each side. Its frustrating if your trying to clear a path wider than the bucket. If you want to push the pile off the road you drive off the road. I have pushed lots of snow with a backhoe.
You can get them with detachable buckets and 3rd function. However they are rare and often $$. Another option is to make something that mounts on the bucket and use 3rd function or a diverter to operate it.
They have rear lockers as a standard feature and most the newer 4wd ones have an automatic locking front differential. They plow great up hill because they are so heavy.
You cannot attach 3pt implements to most industrial backhoes. (not sure what a gravel rack is)
You could use something like a road maintainer if you fabricated a rear hitch. They work like a land plane.
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Your description of the property make me lean towards a full sized 4wd backhoe. It will handle the rock the best, can handle major wash outs, repair the dam, plow snow, etc.