I don't see much need to address the specific problem of a member dying. It's a given that dying means you're no longer part of the pool. If the pool wants to admit a former member's spouse, that's no different than adding any other new member.
As far as somebody dying while in possession of a winning ticket, I'd lump that in with the plan for all tickets purchased by the pool. Once the pool buys tickets, the tickets need to go somewhere safe, and the pool will need to figure out where. Having the ticket lost or destroyed is probably just as likely as having the person in possession die, so what's the plan if Fred from accounting loses that $50 million PB ticket? If tickets are to be held by one of the members, that person's spouse should be aware of it. Of course there's still the chance that they and their spouse (and all 14 of their kids) could all die in the same car crash, but what are the odds that the pool will win more than a few bucks and the person holding the winning ticket will die in the week between buying the ticket and cashing it in? If a pool wins anything substantial and feels they can't submit the ticket right away they should put it in a safe depsosit box, because leaving 100 grand in cash (and a winning ticket was cash if it got lost or destroyed) in your desk is just plain stupid. A small safe deposit box can be rented for as little as $10 a year, which is cheap enough that it's not a bad idea for a pool to rent one as part of their overall plan. Be aware thatin some states the bank must refuse entry to the box (possibly except to locate a will and/or document the contents) if one of the renters (you wouldn't be dumb enough to have only one person authorized to access the box, right?) dies. Boxes can be rented to entities other than individuals, so the pool could rent one as a partnership, which may offer a bit more protection in the event that one of the people with access were to die. In the extremely unlikely event that your pool wins anything substantial and one of the people with access to the box dies while the ticket is in the box somebody else with access should get the ticket ASAP, anyway, just in case.