It needs to mow approx 3 acres, uneven ground, grass (Of course) plus be able to cope with bracken, the odd bramble, balsam. – no problem
Large collection hopper that’s easy to empty – self empties
Robust/Can be given some tough love – give it some love
Easy maintainence – can keep outside all weather
Wide cut – hmmm
Good product support/warranty – free replacements if you breed them
Cope with bumpy ground. – in it’s element here
Powerful – 1 sheep = 1 BSP
Manouverable as needs to cut around trees in an orchard, picnic tables, posts etc. – yep
Cope with slopes well without tipping over ( ) – no probs
Added bonus (If such a thing exists) of use as a small tractor that could tow a trailer (Nothing massive, think less than a Gator load but more than a couple of barrows full)- you’d need to improvise here
I think you just described a sheep, except for the last part, for that you could just attach a trailer to a sheep.