You do whatever makes you happy.
IMO,the 25-06 is already overbore .That means you can't utilize all the powder space you have.
I suppose in theory if you look at the books,you see you can get a bit more from the Wby,but not that much.
Aside from the gunsmith bill,which includes modifying the boltface,etc for a belted case,and making sure it all feeds.Are you going to shoot factory,or load?Add dies,brass,etc.Price them.
You are going from a fairly common brass and ammo,to an exotic.
Now,exactly what is it you can do with a .257 Wby that you cannot do with a 25-06?
Dreaming is fun,isn't it? Getting it done can cost a lot of money.You could spend that shooting your 25-06.
The skill you gain might make your 25-06 better than the 257 Wby.