Power trunk is one of the things I miss from my Model S.
Looks like a company in China has come up with an aftermarket kit to convert the M3 to a power trunk with gesture control (foot swipe under the car). Per the video, works from the Tesla app, key fob and screen too. Sounds a little pricey, but I guess for what you get and converting a car that doesn't have a power trunk, it's not too bad. Does look like a pretty complex install though. Certainly not as easy as putting stronger struts in. Going to have to be something you really want to take it on. As much as I'd love to have it, not sure I'd do it. But, just sharing for anyone that really does want one.