Currently with the way the game is, this will cause issues. While this option looks nice, it also hinders group play more. "Why should I have to deal with realtime adjustments if I can just go solo and lock people out?"

With realtime action, you have only two options, sit there and die while messing with your menu... or try to choose a place with downtime in the level that you can do what you want at. Typically I see an area where you can take a rest stop at least 2 times in a level. This produces internal difficulty with the game because if you want to chat with friends or explain a situation (which I'll assume would be the primary reason you'd like a pause option in solo, since messing with the options screen typically doesn't take much) you have to wait until you're in either a cleared or unoccupied room. Honestly there're enough stopping points in the game if you actually look for them. The floors aren't exactly in time attack mode.

Haven't come across a single point in SK where I thought, "Hey, I wanted to relax there a little more." or "I wonder where I can find the time to make my sandwhich?" Because when you clean a room out or even are gathering crystals (if you've killed everyone you've come across leading up to them) you have that time, that little semi-safezone where you can take a break and do what you need to do.

Where's that picture I'm looking for? AH!
HERE IT IS!!