Probably be alright depending on what kind of work you are doing.
An average full size rig is basically 7 feet wide without the mirrors (add another 3 ft. almost if you own a Ram or Super Duty and feel the need to drive around with your tow mirrors out, but mirrors can be folded so we'll work with 7 ft).
So that is an extra 7ft of room per vehicle in each bay or 3.5 ft on either side of the vehicle. If you are going off one wall of the shop you will have roughly 3.5 ft from the wall to the first vehicle, 7 ft of vehicle, 7 ft between those two, another 7 ft vehicle, 7 more ft between them to the third vehicle and then 3.5 ft to the other wall or more if you are open to the rest of the shop.
Unless you have multiple people working around each other you should be fine.
Id put the lift either in the middle bay so you can pull the two outside vehicles out if you need more room or in the third door from the end assuming you will NOT have a wall along that vehicle and that way you have loads of space beside it and can just pull out the middle vehicle if you need more room to that side.
Not sure if that makes any sense to you but it does in my mind
10 ft. doors will be enough unless you are pulling your 3/4 ton pickup with giant mirrors in and out all the time. It will still fit fine but you will want to pay attention to what you are doing going in and out.
Not sure what kind of farm equipment you are talking but if you have a decent sized tractor with duals then a 12 ft. door is going to be TIGHT.