Unfortunately no. The DLC vehicle files are "locked" in one large file that only the devs can access.

Well that sucks, I hate how restrictive modding is in this game, compared to like flatout 2 back in the day I don't understand why the devs don't open up the moddability of this game then we'd get better and bigger workshop mods like more custom cars, custom game modes, sound effects and graphics and even performance impacting parts like new armour etc..

Originally posted by Krakenous:

Well that sucks, I hate how restrictive modding is in this game, compared to like flatout 2 back in the day I don't understand why the devs don't open up the moddability of this game then we'd get better and bigger workshop mods like more custom cars, custom game modes, sound effects and graphics and even performance impacting parts like new armour etc..

It is very open,other than DLC stuff,much more so than most other games with mod supports.
Theres just some limitation for IP reasons. E.g its very hard to add a new visual part to a existing car you didnt make. But if you made the whole car yourself,no restrictions and very easy to add more parts. You could add a new engine file in about 5 minutes in comparison.

Another example. They recently re-released the audio modding guide. http://community.bugbeargames.com/threads/engine-audio-modding-bundle-wwise.13374/
It tells you everything you need to know to create custom engine sound banks. But if you cant provide your own sounds for that sound bank, then there is nothing you can do.

So its not restrictive at all, just not 'easy' without time,learning and understanding.