There's the .25 Winchester Super Short Magnum (WSSM). It's a very fat (.300 WSM width), very short (.223Rem) length cartridge thats supposed to perform similar to the .25-06. It could, however, already be going the way of the dodo. I wish that Winchester had just domesticated the .25-308 wildcat rather than introducing the .25WSSM. If they had it'd definately be my next rifle, and I bet it'd been a whole lot more popular than the WSSM as well. A modern, high performance short action .257cal cartridge is overdue, and I can think of no better case to base it on than the .308Win.
But I'm like you and not going to do a wildcat either. I've considered going to an Ackley Improved (.22-250 AI to be exact), because it just involves fireforming loaded .22-250 Rem ammo, but I'm not interested in necking up/down.
The .250 Savage (parent case of my favorite CF cartridge of all time, the .22-250 Rem
) would be a great option if you could find it in current production rifles. I know of no company that chambers for .250 Savage. Maybe T/C in the Encore, but I don't know for sure.
Mike