I would do a brine. Use 40% of the meat's weight in water as the brine, then use 1.5-2.5% (depending on personal preference) of the meat weight plus the water weight in salt. For example, a 10lb loin weighs approximately 4500 grams
4500 x 40% = 1800 grams
4500 + 1800 = 6300 grams
6300 grams x .015 (1.5 x 100%) = 94.5 grams salt (sausages are 2-3% salt by weight for reference on salt preference)
I would also add 1-2% of the meat + water weight in sugar (white sugar, brown sugar, maple syrup, honey, etc.)
This is called an equilibrium brine. It takes longer than a regular brine, but your salt quantity will be exactly known and even throughout the meat. Plan for 1 week to 10 days brine time.
Then roll or stuff as you see fit. I did one with puréed mushrooms and apples, sautéed in butter, them added herbs (could be thyme, rosemary, bay leaves, onion, garlic, etc.,) and breadcrumbs until the right consistency (not quite as thick as peanut butter, and remember it will thicken as it cools).
You may also consider cutting a 7-10lb loin in half. Two 5lb pieces will cook at the same rate as one 10lb piece but might fit better on your grill (cooking time is based on thickness of meat, not weight).