Chris,
The logging between 2.x and 4.0 is different. I can get into some specifics, if you'd like, but for now, no there isn't a way to get both to work at the same time without significant structure changes.
If there is enough call for the 2.x, I will reintroduce some code that I started. It would then be a choice of the Admin to insert the correct version.
Is anyone else wanting the 2.x engine?
Eric