couldn't it still be done in order to co-witness? just thinking the magnifier can sit overtop the sights, and when slid to side, you could pop site up to co-witness with red-dot.
Yes, you can & that is how my AR is set up... with an Eotech & their 3x magnifier with switch to side mount, Eotech co-witnessed with my Troy folding BUIS.
Truth is, with an AR platform you can do most anything you can dream of. Question becomes, what do you really want to do with this gun, and why. I use a magnifier on my AR because that is my home defense/survival gun & due to the ballistics of the .223, it can reach out much farther than my old eyes can see. But even then, I have no plans on shooting like a sniper, so a simple 3x magnifiers suits my needs perfectly.
However, the ballistics of the 22lr means that I'm shooting inside 100 yds, and generally much closer than that. I am zeroed for 25 - 50 yards... depending on my mood or what & where I'm shooting. Even an old coot like me doesn't need magnification for such shooting, so all I use on my 15-22 is the TRS-25 co-witnessed with my folding BUIS. Now some here get a thrill out of punching the smallest hole possible in a paper target & use much higher magnification, even when shooting 50 yards or less.
Point is, each to his own. Some would laugh at me shooting pumpkins from the garden where I would giggle at shooting paper at a range. Set up your gun for how you want to shoot.