The Dink Network

If you want to use the savegame approach, you can also check Friends Beyond 3; it is a 2-part dmod, where you have to change maps when changing; it keeps the savegames and uses that to find out at the beginning of part 2 what your stats were at the end of part 1.

There are quite some bugs in it, though (most not too annoying IMO), so I'm not sure how well this part was implemented. I haven't noticed anything that seemed to be caused by it, but I don't know if I would notice this as the cause.