You can get a Wyatt magazine box that will give you alittle extra OAL for the WSM case
Wyatt's Outdoor Custom Rifles - Magazine Boxes
I used a Broughton 5c 1/12 twist for my 300WSM and since most reamers may be set up for a short throat I'd talk to your gunsmith about throating etc for those heavier bullets. I had mine throated longer for the 168gr TSX did the same with a 270WSM.
I would have the action squared,bedded and good trigger on the 300WSM I used a McMillian stock on the 270WSM a Welcome to High Tech Specialties, Inc.!!!
My only problem with the 200/210gr bullets is the lenght vs need case capacity and it sure wouldn't hurt to give Walt a call and get some loading data and see what he thinks. As to gunsmiths you have some great ones that post on this site.
Well good luck