Translation:The chief engineer is thinking to change the plan.
"Wants to change" would be רוצה לשנות. I reckon your second suggestion makes sense Bodo; or possibly he hasn't even decided yet but is thinking about changing the plan. Ideally a native speaker will join this discussion and confirm whether חושב לשנות means "thinking of changing" or "thinking in order to change".
(PS: I don't know why somebody has downvoted your comment but - so far as I can see - not attempted to answer it.)
Well Vid, I think that in the given translation, the engineer is thinking to change the plan, which means that he is considering the matter. However, your translation means that he is has come to a decision and he is in the planning stage of how to implement his idea.
But wait, “thinking to change the plan”, as Bodo mentioned, might mean that he has come to a decision and his thinking is what is necessary to bring the plan to fruition, the same way the student works to finish her homework.
In order to avoid ambiguity, “thinking of changing” would have been the best translation.