averaging state space dc dc converter
I think there are different aspects involved with your question, and there is possibly no simple yes or no answer. You're talking of a small-signal equivalent ciruit, which is a usual method for modelling of switching circuits, I think. By definition, it's linear but valid for a particular operation point only. If your analysis also implies larger variations of the operation point, the linear model is more-or-less incorrect. You have to find out, if it can give meaningful results though.
Because of this basic limitation, I'm not sure if it's of much use, to perform an accurate averaging of equations. Personally, I prefer simple equivalent circuits, that represent the basic properties of the circuit. For some circuits, that have a basical nonlinear behaviour, e. g. a buck converter in non-continuous mode, you may be able to define an equivalent circuit composed of a linear term and operation point dependant gain. But I don't think, there's a general numerical method, it's rather a matter of intuitive understanding.