Ah. I see now. Thanks for the video.
That is annoying. I almost grabbed one of these when I picked up my last M&P15-22.
I am glad I didn't now. I don' like that at all.
I would definitely swap to a new base. Unless you could drag it off the front and get it off.
I would rather have something that had levers or at least thumbscrews that I could take off without tools so I could use the BUIS.
(I prefer Larue myself, but they are pricey)
To your original question. I would try to look through a MBUS before you buy. The sight picture isn't "clean" to me and I don't like them personally. But for BU sights, it might not really matter.
I am no longer participating in gun forums.