Escape from Witch Mountain was remade twice, once in 1995 and then as Race to Witch Mountain. I can honestly say I have seen neither of them so I cannot comment on the quality.

However, are there any other 1970s/early 80s movies that Disney should remake, hopefully for the better?

The two that come to mind are The Black Hole and The Watcher in the Woods, as does, Something Wicked This Way Comes. I think these are good concepts that had poor execution due to where The Walt Disney Company was at the time.