This is somewhat quaint that in the Den TC and 'gang pwning' coexist with slavers guild, which does not give a fuck about anything, including killing it's members and potential customers right at their door. But what can be done? Give slavers priviliges and create exploits or maybe abolish TC in Den?

The only reasonable solution to this would be excluding slavers guild from the TC area, just like in the Boneyard certain districts are thrown all over the city ruins. In this case - exchange the current slavers guild with some shops/houses/ruins/whatever and create a separate Slavers base just outside the den, with an independant entrance from the world map.
This is the only way to have some racional explanation, why the Den TC gangs aren't in constant war with the slavers guild - Slavers just don't give a damn what is going on outside the premises, just like in Fallout 2
(remember the church quest? This was a great example of how Metzeger treats people of Den - whatever as long as it does not interfere with his business. Current Fonline TC
is interfering with his business)