Although I don't have a winch setup on any of my tractors, I use winches a lot. I use winches hard. Sometimes pulling loads that require a snatch block. Sometimes hanging on a winch cable in a situation that would have horrible consequences if it goes bad.
With all that claimer stuff out of the way let me say this. A 7500lb winch will tear the FEL completely off your tractor, destroying it in the process. Especially if you use the BH or tractor weight/traction (brakes locked) as an anchor. Do not do this!!!! But if you do, post pictures of the end result so others might learn from your mistakes.
If you go with the QA plate idea build an anchor spade into the plate. A piece of old road grader blade would work great. If you don't have that I've saw them made from 4x4" square tubing mounted vertically with the end cut and plated at a 45 degree angle.
Concept is you lower the FEL and if necessary put downward pressure forcing the anchor to dig into the ground. When you start pulling the load will all be dealt with at the QA plate and put minimal if any pressure on your FEL frame and mount brackets.
As to side pulls. You can't do a long pull at a side angle. It will "pile" all of the cable on one end of the spool and you'll quickly have a mess.
After addressing the logistical stresses of this setup I feel I must also put on my "Safety Police" hat for a moment. And let me say, anyone that pays any attention to my postings knows how much I resent the Safety Police. But. My biggest concern for your idea is this. The only way for you to run the winch is from the tractor seat or worse, standing beside the tractor. If things go bad, and at some point they will, you are going to eat the cable, hook, clevis, chain, and whatever else you have in the equation. You can add a cable weight which will help this, but it still makes me nervous. Throwing a heavy coat over the cable can also minimize the whiplash effect.
Remember, you will not know how much stress you are putting on all of the equipment involved until the winch hits it's max capacity and stops pulling. By then you have created a deadly and extremely damaging situation. Be careful out there!!!
Build what appears to be an overkill QA plate with self anchor and not have to build it again. Build a light, cheap, easy attachment and tear the snot out of it and your FEL. It's your choice. Post pics either way.