The issue with Poncirus is definitely not the acidity, it's the 'Poncirus resin', that group of sticky, stinky, bitter tasting compounds. I have cooked some slightly overripe C-35 fruits once, and they smelled
awful, unbelievably awful, from the compounds of this group. I had to cook that marmalade for twice as long as normal to mostly get rid of the smells, and even then the resulting marmalade was extremely bitter.
If acidity was the only problem then you could use it like a sour lemon and make lemonade out of it
So using acidless parents for Poncirus F1s won't really help to any degree I believe, as the 'Poncirus resin' compounds will almost definitely be represented by one set of genes.
I grew out some C-35 seeds, and of the 2x monofoliate seedlings I found so far, 1x had the stinky Poncirus smell in the leaves (this seedling now dead), 1x didn't have the smell (seedling still alive). I'm fairly confident that if the plant can't produce these compounds in the leaves, they won't exist in the fruits either, and so my hope for this seedling is that it'll be a small, seedy and sour orange, but it will retain some toughness and maybe even have some interesting double recessive gene behavior too.
I also believe there is a high chance that the removal of these Poncirus resins from further hybrids will negate a lot of the cold tolerance, as I suspect these compounds may have a dual function as anti-freeze compounds.
