The short answer is No. Actually, that's the only answer.
In order to have enemies in multi you have to use generator cogs and even then, the enemies are in different places on each persons computers. The enemies have to be in sync. And then there's all the other cogs used in the levels. They would have to be redone as client/server compliant. These are the reasons for so few co-op levels.
If I were you, i'd just go dl The boam and toam (sp) level series and forget about all your troubles.