I really like those ideas. even before reading through the post i thought about a glass wall it sounds interesting to have a transparent wall or a reflective turf.
but i did have an idea for a long time for a new pitchfork. basically a pitchfork you get from the archives through another fountain that costs 2 moon glass shards and 1 thulecite fragment and it would be a normal pitchfork except it would have 1 / 2 / 3 inventory slots that can hold turn and when you dug up turf it would replace the turf with one from the pitchfork.
or maybe a glass suit that would have 65% armor against normal creatures but 85% armor against shadows
maybe new ammunition for walter using moon glass (honestly i can't think of anything it would do)
or glassy potion which would turn crops into glass (this one sounds like a hell to implement in post RWYS XD all the different crop stages plus the giant one. sounds like a lot of work that only people designing with wormwood transplanted crops would use (me. I design with them))
oh actually i just remembered for ages i want something like the pedestal decor from ONI in dst to display items (and especially skined items like wicker's end of nigh book skin) and it would be really cool to display items in an elevated pedestal inside a glass container (maybe recipe would be 2 marble 2 glass and it would resemble the actual design from ONI)
maybe you could hammer antlion's glass spike and castle for a chance to get a sketch for them and make it out of the rest of the resources or their glass version would look slightly different to the original one.
yeah that's all i can really come up with rn. I really like all these ideas but some of them might be a bit more off the books / not balanced