I have a Sendero 25-06 as well and it's been a great Sub .5 MOA shooter as well. It's about shot out now. I also have a Sendero 300 RUM.
Tell ya what I'm doing... I just picked up a Vangourd Sub MOA 300 Wby Mag and will be replacibng the barrel with a Broughton 5C. I was going to chamber in 300 WSM
, but after learning about nitride treatment which will greatly extend barrel life, I decided to go with a 300-375 Ruger. IMO, a 7-375 Ruger would be a great wildcat, but will kick a little more than the SAUM. If you're considering hunting Brownies, I think a 7 SAUM might be a little light, but that's your call.
I'm eventually going to sell the Senderos and replace them with Vanguards (Howa actions) because I like them a little better than the 700's. The Sub MOA's also have a good aluminum bedding block stock. The Howa long action is about 1/2" shorter than the 700 and a better fit for the SAUM or even 375. Your feed rails might need some working on for the SAUM - not sure on that and something you might ask your smith.
I think your plan is a good one and if your keep the Sendero you'll be happy. Just thought I would throw that at ya. Another thing to consider is you will have to change bolt faces. If you went with a 280-AI there would be no magazine/feed rail issues and you could use the same boltface and ballisitcs are about the same.