I think this is probably the right way to go, in that it leaves the previous options in place while still eliminating the need to 'grid it,' as it were.
I know we're still talking about movement itself, but I figured while we're brainstorming I'd throw in that we'll need at some point to deal with ranged attacks and area / shaped attacks. Figuring cover / concealment may be less precise without a map, though I suspect that's probably the least problematic. Likewise attacks which can only affect multiple targets when they are within X ft of each other can probably be worked out without a lot of brain wracking. I mention them, though, because however easy it might be, we'll have to deal with them in some manner.
Mostly, though, I had started thinking about things like cone attacks and burst/splash effects. I know in the past I've had to do a lot of grid counting to make sure not to catch party members in one of the above-mentioned attacks. Without a map, I'm not sure how that sort of thing would be dealt with? I certainly don't think allies not in direct melee should be immediately free of the area, but I'm not sure how to determine the threatened area?
