well done Sally for doing the research, it is a fun subject to read up on.
One of the better books on pig nutrition is Nutrition and feeding of organic pigs By Robert Blair
When feeding pigs you need to consider why you are feeding them - Is it for
Speed finishing - get them to weight as fast as possible
Taste - you are what you eat
Leanness - ensuring correct fat covering
Cost - getting there at the cheapest cost.
If it is speed finishing, then grower and finisher is your route, and don't deviate as anything else will be a second best, and not finish as fast.
If it is taste, then outdoor will achieve a totally different taste than indoors, as with the pigs just rooting/grazing and getting soil, worms grubs and vegetation, this will change the flavour of the meat. You are what you eat, and adding fruit/veg will add further notes to the meat. There is an old tale of the farmer who grew onions, and after harvest put his pigs on there to let them root around. They found so many missed onions and ate them, that when the pigs were killed the farmer described them as tasting of diesel !
If leanness, then watching supplemental feeding, and ensuring that carbohydrates are restricted will help, along with regular feeling of the backbone
If cost, then watch that the "free food" is really saving you money. If it takes you 8 months to do what grower does in 4, is this really a saving? Is a twice as fat pig as it has had too much carbohydrate saleable? what about your time or that you could have sold twice as much meat (2 lots in 4 months than 1 lot in 8 ). "Free food" can be made to work, but is not a guarantee of saving money.
In reality we are all balancing the above factors, time, taste, right amount of fat and cost.
At Oaklandspigs, we tend to feed fruit/veg to our sows (who are effectively maintaining rather than growing, so less protein, more carbohydrate diet), and do on a basis of substituting one meal with fruit/veg, and then normal food for other feed of the day.
Last thought - I had a phone call last year from a customer worried about what she was feeding her pigs, spent 1/2 hour chatting through possibilities, protein, CHO's, min/vits etc. During the conversation I heard her saying "just get yourself something from the freezer" - when I commenetd, she said "oh that was just the kids coming in". So her pigs merit several days of her worrying and a long conversation with me, but the kids - well she wasn't weighing their food, noting the protein levels, oil, worrying about amino acids !