Re: New ideas for an old world.

Rather than destroy Toril, what if you used an "alternate reality" scenario?
 The various incarnations of Star Trek have beaten this to death, but it
still works.

For reasons that are up to you, the PC's have been thrown into this alternate
reality, where Toril *was* broken into a cluster world, using one of the
scenarios you mentioned.

One route you could use is a parallel prime material plane. In this, the PC's
wake up one day and realize that everything is different.  Perhaps they are
staying in a small village somewhere, and are en route to Waterdeep.  The
village looks the same, but after they go down the road, they realize that
they have reached the end of the world, and there is a spelljammer port in
front of them!

"Hey!  That isn't on the map!  There's supposed to be a mountain there!"

In this kind of campaign, the PC's may be trying to get back to their own cont
inuium.

If you want to be more daring, use an alternate timeline.  Something "went
wrong" in the past, shattering Toril to bits.  The PC's, perhaps with the
help of a powerful patron like Elminster, are sent back in time to put things
right.  You should only use this if you know the history of the relms
intimately.  Perhaps during the Time of Troubles, a powerful artifact was
mis-used by some wacko wizard or over ambitious Dracolich, and Toril was
blown apart as a result.  Elminster sends the PC's back in time some thirty
or fourty years, shortly before the Time of Troubles, when Toril was whole.
 Their mission?  Find that artifact and *destroy it!*  Elminster might even
send a letter to himself telling himself to send the PC's back into their own
time when their mission is complete, or he could assist using a spell that
lets him communicate with them, sort of like "Al" from Quantum Leap.

Did I lay that on a little too thick?  That's what I was afraid of.  :)

Richard
The Bard of Wildspace