I use filler like corn or tapiaco starch for chili type sauces.
For gravy sauces, I find using mashed potatoes as filler effective too.
Maybe, I should try using sweet potatoes and/or yam too. I did once try mixing cottage cheese after the gravy was done. Which, I recall, was a disaster, both structurally and flavour-wise. O, maybe you could try apple-sauce?
I also find boiling egg plant/brinjal till the brinjal melts into the sauce helpful in holding the sauce/gravy together. I notice that many Indian gravies (aka curries) have mashed channa (chick pea gravy), melted brinjal and mashed potatoes as the "holding medium". Instead of pouring the sauce onto a naan/roti, I pour it onto my pasta.
But then, wouldn't people disdain me for contaminating an Italian concoction with Indian characteristics?
Chick pea gravies (aka hummus) basted with olive oil and garlic are also a very Mediterranean characteristic, which also seems to be a favourite component in both Arab and Israeli casual eating establishments. I don't know, but I think you have to add the vegetable sauce to the basted hummus rather than the other way round, to retain the characteristics of the hummus in a controllable manner - it's my hypothesis, because I've not seen any Israeli/Arab small-establishment chef/vendor (where they cook in front of you) dunking their medal-worthy hummus into vegetable sauce. But since none of them are looking, I am sure you could do it the other way round.
When I say basting, I recall they actually fry it on a pan/hot table-plate rather than basting in an oven.
I find solely using melted brinjal very helpful as a holding medium and does not alter the flavour of a gravy noticeably, except to contribute more towards its being a vegetable-based sauce. First, you need to acquire some familiarity with melting brinjals/egg plants into a gravy thro trial and error.
Oh BTW, that week-old precooked pot of cheap pasta (I bought 95ct a pack from Walmart) in the fridge, you could boil some with your sauce till the stale pasta melts into the sauce. Functions well as a binding agent - flavoour-wise, I don't know.