What I guess I am saying is that using joint tenancy as the primary means of estate planning is a pretty blunt instrument. And it has the potential to snap back and pop you upside the head. Maybe it's reasonable if the dollar amounts are small and the number of potential heirs are very limited.
OK, you aren't going to make all nine siblings joint owners. Just you. That still makes you an owner of those accounts. What happens if:
1) You divorce?
2) You run over and kill a 30 year old investment banker making $1 million a year who has a wife and 3 children?
3) One or more of your siblings predecease your mother? When the time comes for you to divide up that money, will you include the predeceased siblings' spouse and/or children? And, if you do, will all your other siblings be OK with that? Yes, if you are JTWROS on the accounts, they are legally your's upon your mother's passing and you can do what you want. But, will you be OK with any possible hard feelings stemming from your decisions?
(If you are JTWROS on your mother's accounts, I don't know if, technically, it is an "inheritance" for you. But, if you then give your siblings a portion, that is a gift from you to them. Whether that makes any real difference depends upon the amounts and your own financial situation.)