I think agile offers a simple solution to this problem, at least in our company it was very easy to implement.

First, estimated stories are immediately broken into tasks and discussed, which helps all present understand what needs to be done and later in collaboration. Second, the team may at any point request a spike story to research the story before estimating it. This approach solved the problem of different team members having varying experience with a given problem.

Having a familiar member of the team implement the feature will always result in increasingly serious problems later on. Knowledge sharing is essential to agile.