Openings in a old stone stable

[Valleygirl]

Hello, I am transforming a really old stone stable in Ticino (Switzerland). Since the ground floor was used for animal storage (mostly goats), it has no windows, and for the transformation I need some openings to get some light and air in. I am aware of the method of chiseling out stones from exterior and interior and fitting in concrete lintels to make a frame. My question is if I can do the same with wooden lintel frames and if yes, then how big can an opening be? My wall is 650mm thick and the height of the window can be flexible. (I just want some openings). Other than wood, what other (sustainable) methods are there?

Thank you