It's coming along and looking good. The only thing I see that might cause a problem is that the hinged door doesn't look like it will fold back and lie on the top when you open it. It looks like the too/rear edge will hit the top surface when the door is a little past horizontal. It will be awkward to have to hold it or to create something to hold it up. Plus you'll have to reach under it all the time when going "in." I think a piano hinge might be a better plan for the front door. That way you can open it and lay it back on the top surface, out of the way.

You bring up something I've wondered about. If you have a fan pulling air through, even slowly, wouldn't be drawing a draft through the housing? That's what you are trying to prevent to minimize part warping. I don't have a housing and have never used one but I have wondered about it as I consider designing my own housing. Even passive venting at the top somewhere invites a draft because as the warm air exits, something is coming in from somewhere to replace it. I'd imagine that the "something" is cold air from around the bottom edges which are open. Maybe it's not a problem to have a small draft if the bulk of the air inside is nice and warm. I'd be happy to hear from someone who knows the answer.

Personally, I'd rather spend the extra money and have a view from the side. But, it's not necessary. There are times though as I watch a print that I move from side to side to see the area I need to. I can't always tell from the front if things are going well. Also, it can get pretty dark in there. The clear sides will let a bit more light in. Even with no housing I use a flashlight sometimes to view my prints. If the cost of the extra acrylic is just too much for you then you at least put two small, hinged metal doors on either side. At least you could then raise one and peek in for a few seconds.

Nice looking though. Post finished photos...