I don't think Lirin IS a Radiant, but it wouldn't surprise me if he becomes one (of whatever order Ym was) later. I doubt Kaladin's parents (or anyone else) can stay in their village long term, with the Everstorm going around the planet.
I dunno, seems a bit Alethi-centric to me... I'm not sure how often glyphs are used outside of Vorin cultures, and I think many religions in the west are more aligned with Cultivation.