The 356win is all that is needed from 336, its current down fall is a little to much case head pressure. So what about the 300savage necked up to 358.

What can't you do with a 200gr corelokt RN traveling at an authentic 2400fps or a speer 220gr at 2350fps. Moose, elk, bear, and deer real dead real fast and still without excesse recoil in the light 336. This and the 250savage based 308 express, and the real 250savage would be a great trio.

I think marlins customer want cartridges that fit a real need not just ones who's number may look better.
22 bee
250 express
30-30
308 express
357 mag
35rem
350 express
44 mag
444 marlin
45-70 this line up would do it.