Just a thought, unless you need the windscreens often, couldn't you just roll some aluminum foil and push it between the griddle and the housing?
I totally agree the Blackstone is heavy and annoying to carry around, but it is the best way to feed a large group. We try to avoid frying anything inside the trailer, especially bacon, because it makes a mess. The Blackstone is so easy to clean and more versatile than a grill.
A bag is a must. Blackstone uses very good quality ballistic nylon for their bags. I also recommend the hard lid, which keeps heat in and is good for low temp cooking or steaming. It also covers the griddle for storage.
This bag is great for the 22" with stand and lid, although the combined weight is really heavy and cumbersome. I position it with the stand inside in the rear storage, then add the griddle and push it into location, rather than trying to carry it all at once. I noticed the 17" bag isn't designed for the lid and requires you to flip the griddle upside down, which is really stupid. I would try to find a bag that fits everything assembled ready to cook, which unfortunately for the 17" isn't going to have a Blackstone logo on it. Still lots of other options on Amazon.