...ah. Well crap. I've been buying the raw glass for all these years for nothing. Oh well. Time to start buying sand and hope the civilization has rock crystal to trade.
=Uncool-
Well, I wouldn't say it was for nothing. Glassmakers use raw glass for moods, you can have jewelers cut and decorate with it to avoid using more valuable gems and stone, and creating cut glass gems satisfies mandates for noble who like that type of glass.
Floor Grates will do the trick and can be made from most materials, the only catch is that floor grates must be supported orthogonally (aka diagonal won't work). Depending on what your wanting to do building floors with a row of grates followed by normal floor repeating you can have multiple animals watching for ambushes and since arrows can't go through grates they are perfectly safe.
A more efficient method is like this:
+++++++
+##+##+
+##+##+
+##+##+
+##+##+
+++++++
You can alter the size as needed of course. Just repeat the segments next to each other to widen the viewing range.
With a support connected to the floor above, you can also do this:
+++++++
+#####+
+##+##+
+##S##+
+##+##+
+#####+
+++++++
Attach the support to a mechanism and you have a handy defense mechanism on top of everything else since the middle three floors and the six middle grates will all fall if the support goes.