Someone asked earlier about cowboys co-existing with the gold rush and that maybe that should be left for DCA.
They did co-exist.
My only problem with adding stuff to Grizzly Peak is that it is set in present-day.
It's Grizzly Peak Recreation Area and the play area is themed to today and so is the rafting expedition.
Frontierland is old. It's themed to old west and is meant to "turn back time" (yes, that was a Cher reference).