BA jumpers are already behind when rivers, lakes and pools are automatically at least difficult terrain which means dangerous for jump pack marines. You might as well insist that you use the Mysterious River Table because you might be able to squeeze some benefit from it.
1- no change
2- loss of warp charge points and no Deny the Witch rolls
3- add the Feel No Pain rule but need to pass a leadership test to move or shoot
4- dangerous terrain, vehicles immobilized is automatically wrecked
5- 5+ cover save, going to ground is a dangerous gambit
6- dangerous terrain, re-roll failed armour saves
Essentially, there is no downside to using Mysterious Rivers when using jumpers. Mechanized lists have really little to gain, though. Think about getting some river terrain into your games to balance out with the buildings and blast craters; it might turn the battle in your favor.
Jumpers treat difficult terrain as dangerous terrain (Rule Book p.47). You have to roll a 1 to trigger it though (Rule Book p.90). Then you still get armour saves and a Feel No Pain roll too. Dangerous Terrain is far less risky now. Remember, your jumpers can also land on impassable terrain if they physically fit and they treat it as dangerous terrain (Rule Book p.47). This may come in very handy for Deep Striking and jumping onto unusual terrain features, etc.
If anyone has great ideas or experiences, always add them in the comments to help Blood Angels players.