Of course you hold a camera with two hands, you can hold a camera with two hands and it still feel squished together.
I would take a mirrorless camera in a DSLR's body form. It would still be lighter. Could even be given better battery life as a result.
But EVF's need to be better in low light, which after sunset, just before sunrise and astrophotography, hell even in the city street with no direct sunlight would give you problems.
Give a accurate colour display, even with OLED the human eye sees more colours than even a rec. 2020 display, which still don't exist yet.
The auto focus needs to be faster, 1/2 a second longer to focus? So even the best lenses focus like a plastic fantastic 50mm 1.8 on a rebel camera? Hardly what you would call $1000 worth of lens.
As a wedding photographer that would seem a massive step back, the OP is talking about static subject mostly so perhaps that won't matter for him.
I do understand that once the bodies get better auto focus that problem will disappear.
I can put a lot of old lenses on my canon camera, and while I have enjoyed playing with them, they are better than modern consumer lenses, but the professional lenses from Canon, Nikon Sigma etc. are better still and have AF. That's a huge bonus for professional work, personal work I guess it would be down to taste.
Not having to carry a few filters? I have yet to see a picture shot into the sun that can actually capture the dynamic range without blowing highlight or losing shadow detail, never mind having to have the printer capable of printing such a large dynamic range.
I do understand that mirrorless might be the future, I just don't believe we are at that point yet.
You could work around the other issues, buy a grip, extra batteries, invest in some patience, be willing to occasionally pre focus and spray and pray, but you have to get on with the type of viewfinder or it all falls down.
When I got excited and had the same thought as the OP the EVF was the line in the sand.
Yes the banter is good, if you have two sides of an argument then the OP might have a better chance of an informed decision either way.
Can't be having the sales and marketing goons at the local camera store misinforming you, just to make a sale.