Welcome to the forum and that's a very interesting question.
If I were to attempt an approximate and unsatisfactory answer myself, I would begin by saying that, these days, most people seem to me to be less troubled by what he calls celestial realities (particularly the gods) and death. Because of this, I imagine that if Epicurus were to write books about nature today, it would be primarily to fully understand the limits of pain and desire (especially in the capitalist society of overconsumption in which we live). Furthermore, Epicurus would write about the Canon.
I suppose it would be necessary to evaluate the context in which one might imagine Epicurus appearing and how he would arrive.
If you were to literally have a time machine and transport the literal Epicurus, he would have a lot to do to pick up where he left off and decide how to evaluate what had happened in the intervening 2000 years. And if you allowed him time to investigate the history of the intervening time, I suspect he would be very unhappy about how society and social structures had developed during that time.
When he left, Epicurean views were young and gaining popularity, as they did for hundreds of years after he died. The views that the espoused on most major issues of life were well respected and even opposition was within reasonable limits. Much of what has happened since that time represents a setback for those views, however, and I suspect that first and foremost he would want to know "why" and "what happened" to prevent the continuing development of his nature-based viewpoint.
So in the most general terms I think "catching up" and then diagnosing "what happened and why" would probably be his first step. Then depending on what circumstances you placed him in, you'd probably have his attention drawn according to those circumstances (rich, poor, peaceful, at war, etc).
That's only a general initial answer but thanks for your post and welcome to the forum!