I want one too even though I just did a 25-06 and know that in my hands I won't gain much as I rarely shoot past 400 with 300 being more typical. Twist rates: my 25-06 is 1 in 9 and I would do the same for a Weatherby. In the 06 and smaller 25s some 110 and heavier bullets will not shoot as well as the lighter ones with a 1 in 10 twist. The velocity might make up the difference but it might not especially with 115 and up VLDs and custom heavy weights. But many only use the 100 grainers and 1 - 10 is fine for these.
Although I know it is not true I feel like a 24 inch barreled Weatherby is a loud 25-06 so I would go 25-28 inches especially if in a single shot for the longer barrel. I could see having a light weight 25-06 and a medium weight Weatherby as a good combo depending on how much stand hunting versus walking your doing.
My one uncle had a .257 wby with a 28" gain twist barrel that was a velocity over achiever, With less then full bore loads it was plenty fast and very accurate. His was a short throated camber that was a demon on the Ghog population with 85 gr BTs
