7STW…really bad choice. No brass, no data with new powders, no dies, no factory ammo, AND a 3.6” mag box isn’t long enough for new bullets.
28 Nosler…brass hard to find and expensive when you do, plus you will need to “adjust” the action’s rails, follower etc with no guarantees that it will work as well as it does currently. No availability of any factory ammo.
7 PRC…unknown future, no brass, less powder capacity than what you currently have. Can’t rechamber current barrel. I realize you aren’t considering that one but it was mentioned.
7 RM…popular, widely available, needs to have the throat extended nothing more. BINGO! Just stock up on components and wear out the barrel.
No arguments on your post but would like to point out that Peterson make brass for the 6.5-300 Wby & 300 Wby, both can be easily made into 7mm STW
Peterson also make 340 Wby brass that can be necked down with a few more steps
It would appear that the 7mm STW never had better brass available in it's lifetime
