OP I think you're on the right track, actually, I DO have kids and also think that 'banning' / controlling foods is not that healthy for them.
My kids are 3 and 4.
Since they are still young I do 'control' food to a certain extent in that I only really offer them healthy options, I don't actually keep things like soft drink / sweets /chocolate etc in the house that much, so don't eat them myself regularly either.
But they do choose and control what they eat themselves from what's available.
Their usual snacks that are available any time they like, are healthy ones, such as crackers and fruit / veg.
I keep their crackers on a shelf they can reach and they can help themselves any time. They don't really make a mess, IE get everything out, or waste it etc. They'll leave crumbs, but they would if I was allocating snacks to them too.
At least once a week we bake together, either cakes or biscuits. I never restrict how many they eat of these. I've explained, and they've discovered for themselves, that too much sugar will make them feel sick. They self regulate their intake of these themselves with no problems. I think because they could have as many as they want, they don't feel compelled to. Typically my 3 year old will eat 1/2 a cupcake in a sitting and my 4 year old 2.
Same with sweets. We don't have them that much, mostly when we go to parties and so on, but they help themselves when we do have them, I can give them a whole bag, and they won't scoff the lot.
Again I think that is purely because I have NOT been controlling what they can have, that they are able to do that.
I agree with you that by regulating their intake, it is not giving them the opportunity to work out how to do it themselves. Mine have been helping themselves since they have been physically able to do it, so it's not true that even younger children are not capable of self regulation, they absolutely are.
As they get older and can buy their own treats / junk food, I fully expect that they'll then be able to manage that themselves without any input from me.
With regards to snacking between / potentially spoiling meals, I don't have any issue with that. Especially since they are snacking on mainly healthy foods they often eat better with their snacks than they do in a meal, they certainly get their 5 a day in easily from snacking.
I tend to cook fairly small meals for them, since I know they snack a lot, so I don't usually get waste. I think it is actually better for metabolism to eat more often as well. Both of my kids are on the thin side of average, so snacking all day has not been detrimental to their weight at all.