In this case I would say no, it is not possible to mix these, or at least not worth the hassle.
If the robot you were trying to add has custom components that you have not also added to the game, then the robot will not work. If you wanted to add the RW Thermidore to DSL 2 you would also have to add all of the components Thermidore uses to dsl too.
Also if you are adding robots from the RW mod, which is for DSL 3, to DSL 2 you are also going to have the problem of all the DSL 3 components that are not in DSL 2.