The method I've always heard for ripening fruit is to put them in paper bags or packed in
cardboard boxes and covered with paper, to keep the ethylene gas somewhat inside and let moisture out and
enough air exchange. I've seen that putting a banana in with them produces more of the ethylene gas that ripens them, in case they are not producing enough of it themselves.
If they're really too green to ripen, you could try making chutney. I've made chutney with green apricots, and it's pretty good. We make it like making jam, but as well as sugar, we add salt, powdered or flaked dried red chillis, and either garlic or asafoetida (
hing). It's got that sweet-sour-spicy-funky thing, like what makes southeast Asian food exciting.