Just wondering if anything can ever be done to improve the turning radius of these slow cornering pigs?

Fast pace you don't feel it, but it's a definite problem in slow speed parking areas.

Tried finding something on tuners, but no-go. There has to be SOMETHING that can be done to improve a little.

Yeah, you need to modify the knuckles, google mustang drift knuckles, you're basically looking for something like that.

Only thing I could see being an issue is the AWD system not working at the same rate (more turn, less movement for some wheels).

Your diffs are still all open so that doesn't matter, even with an lsd you'll be fine though it might do some funky stuff at full lock depending on what style lsd you have in there. I also can't see the rear being an issue, would only be the front and center that would change how they work.

I'd be more concerned about the CV joint angles than I would be about any possible momentary differences in wheel speed, and since no DSM diffs are locked (or lockable), there's nothing to worry about (with regards to wheel speed differences). Even if you had clutch-type LSDs front and rear there'd still be no real concern.