Yes, that would be a really bad idea.
We would basically end up with unoptimized crap like AC:U for every single game,which probably wouldn't get fixed until 6 months from launch LOL.
But if I was given the choice I would choose PC,since I'm mostly a PC gamer,well recently I've being playing more on my Wii U and XB1, but I still prefer PC.
As of right now we have nothing on PC, that can compare to some console exclusives in terms of textures and lighting.Thus I'd really love something like that on PC.Why?, well it is a no brainer for me,I'd take 4k over 900p,1080p anyday,for god's sake I had a 5760x2160 rig not long ago,thats 1080p x6.My biggest concern when it comes to graphics is AA.The game I'm playing could be running on DX9, but as long as it has no jaggies,and I mean NONE at all, that no matter how much you zoom into the image you would find no jaggies,that's already eye candy for me,and that is only possible on PC with SSAA, and SGSSAA.I bet I sound like a crazy guy right now lol, but when you build an enthusiast level PC and try the highest quality of AA, it just doesn't feel right playing a game with a lesser alternative of AA.So yeah for us graphic enthusiasts(or graphic hores if you want ) who can stay for hours admiring the graphics, PC is always the way to go.
Anyways, you are right it is not a good idea.Basically all games would be third party,and lets be honest, nowdays even on consoles third party games aren't exactly optimized.Basically it is as you said, exclusives have to stay, most of them are outstanding in every aspect because developers are rewarded exceptionally,if you take that away,there would be no reason for them for going the extra mile.