Interesting ideas but, if he shot her, wouldn't he have used her own weapon if trying to stage a suicide (a version that's been floated and not sure where that came from) ? Allegedly, KK wasn't there yet so MG's gun couldn't have been, either. So the the story goes, anyway. Since her body was not left there, the staged suicide would be a no but shooting is still possible.
However she was killed, I still can't fathom how blood was spread all over the condo. One swing of a bat would knock her out and a bullet to the head would send blood spatter in one direction. Both methods would be very bloody but contained to one area, I would think. So far, I've read blood in the living room, kitchen, upstairs and bathroom. Bathroom could be entirely due to personal and/or condo clean up. He may have gone upstairs to get something after killing her, hence bloody footprints up the stairs and in the loft. But, the kitchen and living room are a large area for blood spatter. That's too widespread for a bullet. Multiple swings of the bat (back and forth), with blood on the bat, could send blood flying in both directions. The thing is, after the first hit, it would seen Kelsey would have been on the floor and it would be hard to keep swinging a bat at her. I just don't know. I'm also sorry to be laying out a visual of something so terrible but it's relevant.