I have the 375FL, almost identical to yours with no loft. I've admired the 376 and 377 since they came out. They didn't exist when I got my 375.
I never thought about there not being a window in the loft. Maybe the manufacturers figure with the back door right there by the bathroom and steps that go to the loft, a secondary escape from the loft is not necessary.
But really, I've never thought about that.
Actually, when thinking about it now, many campers that have a loft don't have windows in the loft. Maybe that's why they always give me a claustrophobic feeling. Great space for storage, but not so great for sleeping in my opinion.
If you want a window up there, first, is there enough height to put one.
Second, if you put a window up there, the frame around the window will have to be built to support the joists holding up the roof. That means the skin of the camper is probably going to have to be removed to rebuild a hole. It's not just a matter of cutting a hole and slapping in a window. That hole has to be re-inforced to support, not just the window, but the integrity of the rest of the trailer.
No, Keystone is NOT going to put a window up there. You are fighting a loosing battle. If you want a window, you're going to have to take an alternative path and do it yourself, or hire someone to do it for you. Either way, you'll but shelling your own money out.
But here's a suggestion? Rather than installing a window, why not cut a hole in the floor of the loft with a trap door. Open the trap door and the kids up there can fall down on the bed. If there loft stairway is blocked in such a way it can't be used, that back door is useless anyway. There's the window in the master bedroom. Cutting a hole in the loft floor can be done between the floor joists and not affect the integrity of the camper at all.
And while we're now talking about the master bedroom, I wonder why Keystone did not put a window in the slide out at the head of the bed? I would love to have a window there.
I just looked at some photos of the 376 / 377 model on-line. There is a window up there, Even if it opened, is there enough space for anyone to actually crawl through it, and if they did, that's a LONG drop to the ground? To do it right, the entire window would have to be changed. The trap door may be a better solution.
2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually