Personally I don't know the complications that would arise, and if the Authors would go with the idea. I see some benefits from this if both projects were to be combined into one giant adventure:
1) Consistent characters (no need for duplicates of the same character)
2) Keep consistent weapons & armor from Drizzt Saga to RoT.
3) Chance to eliminate old bugs (hopefully new bugs won't appear).
4) Chance to eliminate any lingering conflicts with scripts, items, creatures, etc.
5) New Banter (for consistency purposes)
Possibly other benefits I'm not seeing? Also the combined mods will need a new name...
Also making Drizzt Saga & RoT as being optional components if you just wanted to play the BG1 Quest line or just the BG2 Quest line, but doing so would require a small story change.
So this idea good or bad? Honestly I don't know the real inner workings of how these mods are made, and what it would take to do something like this, and if it even is practical.