I could have misunderstood what I have previously read, but can't already share content between six Kindles on the same account at the same time? I would imagine that covers the size of most book clubs...if not then two accounts and a couple copies of each book should cover it...assuming I understand the Kindle TOS correctly.
https://wiki.mobileread.com/wiki/Kind...Amazon_account
I imagine that is one of the things which puts a Kindle a but higher up the list for a lot of book clubs...but don't think that B&N is not doing this for a profit at the expense of the device owners, they will charge more (over the single copy price) for "club licenses" and probably by a fair amount.