12.5 acres. you might be hard pressed. to get a backhoe. if it was mainly all woods. and you were wanting to clear them all out. you might be better off renting a dozer.
if you were just removing a stump here or there, you might be better off just renting a mini excavator. for a day or two. (save up projects, and then get them done all at once with a rental of mini ex)
backhoes do place center of gravity higher on a tractor. and as a result can increase chance of roll over.
on other hand, i can't live without the backhoe. to many uses come up. here on the 80 acre farm.
sub frame and going third party backhoe vs bought with tractor. not sure why all the big deal is, beyond wanting a seat that does 180 swivel, but if you are rarly using backhoe. any backhoe should be good enough. even if it means a little mod to sub frame, (normally drilling a couple holes if needed at all)
if ya only going to be digging a handful of trench. it might be better just to rent a ditch witch, or trencher. or mini excavator. more so if you already have a full size truck with good hitch. pending on were you rent from, you might be able to rent trailer at same time if a trailer is needed.
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FEL (front end loader) would most likely serve you will. and if no backhoe. would encourage a bolt on tooth bar from the front bucket, to make it a little more easier to dig with.
with FEL, you will want some sort of "rear ballast" to max full use of lifting capacity of the FEL. in most cases. not always, so either loaded rear tires (fluid in them), rear wheel weights, or 3pt ballast box / weight box, or a heavy piece of 3pt equipment like a box blade or rear blade. a backhoe can work as well as rear ballast for the FEL.
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30HP tractor most likely max size you will need. you may not be able to unload say a full pallet of bricks or lumber off of a trailer or truck that delivered the pallet of bricks or stones. but lift height might be there. to say load the FEL up with shingles and raise FEL bucket up high enough to off load a few bundles of shingles at a time on a low point of the roof.
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tire types. you noted mowing going to assume finishing mowing (like around your house) vs using a rotatory cutter (bush hog) to deal with tall weeds. finishing mowing, is going to most likely put you away from R1 ag tires, to either R3 tires, or turf tires. you may not be able to find a tractor used that has R3 or turf tires and size that you want. tractor tires can be rather costly. and pending on rims and tires on used tractor, may mean needing new rims as well to switch to a different tire type.
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if ya goto kubta, or deere or newholland website, i think they all have a "tractor builder" thing you can go through. to build your own tractor. a lot of the "optional accessories" TNT (top and tilt) for 3pt hitch, rear and front work lights, 2 rear hyd ports on rear for 3pt hitch. etc... can become very handy.
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4wd OR MFWD is always nice. but having "split brakes" for left and right rear tires and differential lock can come in very handy. some manufactors have some funky setups of were the splits breaks are compared to the gas pedal / go pedal / HST pedal. for me i use split breaks enough, they have to be on opposite side than the gas pedal / go pedal / hst pedal. make it for dealing with snow, to muddy situations to sharper turns when in 2wd drive, to other.
