Question is, what's the anticipated need for the down-the-road LA magnum?
ELR target? LR hunting?

You can always put together a LA in .308 by getting something like a used .30-06 and screwing on a different barrel- then swap out the bolthead and barrel later.
But there's plenty of SA capable chamberings with enough energy for Elk as far as you'd feel comfortable taking the shot, and steel to beyond 1K.

The large magnums can be more difficult for some to shoot accurately, so unless you need all that boiler room I'd consider other options.