Well in the plains some bridgemen are says to glow from stormlight, so i suppose that they are a squire and no little-surgebinder.
Then seems that Lopen don't have a Spren-bond, or at least he never speaks with is "spren", Lopen thinks to could use the stormlight to put somebody at the wall. The only Radiant with the Adesion power are Windrunner and Bondsmith.
I think we could put out the Bondsmith of the discussion, and Syl says "I'm the only Honorspren, to came in the Physical Realm".
Maybe is not a 100% sure prove, but at least I think is more plausible for Lopen to be a squire.
PS: Sorry for the poor English