A lot of what the swamp places is static, as well as Map tiles, Have you ever seen a swamp2Forest transition on OSI?

basicly, (I could be wrong.. it has been known to happen.. i think..) you have a couple options..
1) you could try to edit your Dragon Scripts to only place the Map (landscape) tiles, and not place any static tiles.. Dont think that will work though..
or,
2) You will probly need to make a 2 tile border of grass 10, between your swamp and Forest. but then you would only get the hillside transition, no cliff. and would need to add in the Grass bump as well.
Basicly, you will probly need to do a bit with World Forge, map Edit to complete or finish the job, wich will be dificult since the swamp tiles show up as black. (at least for me)
Hope that helps some, and will try to think of other solutions as well..
Maybe Ryandor has somthing more, and better for this.