"How big a tractor for road maintenance on a long, steep road, bush hogging, tree removal, build site preparation
and more. What implements and why? What hydraulics and why?"
Outside of your building site and the ground occupied by the road, what use will be made of the balance of your 73 acres?
A Rotary Cutter, Bush Hog brand or other brand, is good for keeping land clear and mowing saplings, but how much land will you be cutting? Which returns us to: what use will be made of the balance of your 73 acres?
I will start you off:
Front End Loader (FEL) plus optional heavy duty bucket for your rocky environment.
Telescoping Lower Links on the Three Point Hitch + rigid, pin-adjustable Lower Link stabilizers.
Triangulated Cross Drawbar for the Three Point Hitch for towing tree trunks and trailers.
Suggestion:
Tractor Quick Hitch-Cat 1 Quick Hitch | Agri Supply #61559
Ratchet Rake attachment for your bucket= brush removal, piling brush and moderate grading.
(Ratchet Rakes are sold by the T-B-N store.)
Ratchet Rake VIDEO:
https://www.youtube.com/results?search_query=ratchet+rake+brush+clearing
Skid Steer Quick Attach (SSQA) option for your FEL. Makes taking off bucket easy. Required for a grapple.
Grapple for tree lifting. Requires optional rear hydraulic ports. (Hydraulics for the Three Point Hitch are standard.)
VIDEO:
https://www.youtube.com/results?search_query=compact+tractor+grapple
One professional quality chain saw. I like my relatively light Stihl MS261. A battery powered reciprocating saw with "pruning" or "axe" blades.
Rotary Cutter - width and weight to be determined by potential use.
A roofed Utility Vehicle with a rear hitch combined with a DUMPING trailer.
Steel toed boots, safety glasses.