LF is a much more important production site than Imelda's (now). And a single Warrior will still be a bit risky. Besides moving him out would require us to raise lux to an almost forbidding level unless we cut food production at LF. lux connect is 9 turns away. Cheapest solution is to move the warrior from Imelda's, wait for the next Settler and send him to whale, let the fog busting warrior move on Hef's and swap with the current MP there who in turn follow the next settler north to settle. Moving him to LF will be 8 turns until he arrives.
EDIT: Warrior on Mountain will only make the Barb bypass him anyway so only reason to have him on it is if we have another warrior ready to attack the barb when he enters the plains tile. I agree we need to herd barbs into open terrain when possible and with the amount of mountains we get enough waring so we can move a Warrior on top of the mountain if and when a barb appears..