I guess I get to be the first to say "Welcome!" Somebody who knows what they're talking about will be along soon. For now...
Assuming that: a) you don't want any new switches b) you're talking about giving up the parallel combination c) you can live with a hanging hot here and there.
you could do this:
otherwise, if you're looking to add the series combination to what you already have, you can get a tele 4-way switch (I swear I don't work for them, you can find this schematic all over the web, this just happens to be the one I've bookmarked). Alternatively, somewhere in this thread they ended up with a "series over-ride" switch which would allow you to keep your 3-way and replace one of the pots with a push-pull.