Ho, you might go for a mobile port huh? Understandable. With the current controls, the game does in fact scream "touch screen". I've just tested it on my Samsung Galaxy S10 (Android) and it works since it's a WebGL build! The snake is indeed easier to control this way! Do you still want to have a dedicated mobile build?
About the limitations you've mentioned, yes it's fair. For these kind of games, "why should the player play again" is really a key point and the player usually stops playing once he feels like "he has seen everything the game has to offer". Adding more power-ups and more enemy hazards would be indeed a way to increase the lifespan of the game.
Honestly speaking though, are you sure about aiming for the mobile market? 10 years ago there weren't that many games on mobile so a lot of small but fun games could make it big like Doodle Jump, Angry Birds, Temple Run, Flappy bird (and so on). Nowadays though, making games and shipping on every platform has never been easier so, competition is at an all-time high. The Google Play Store is now flooded with games, both short and long and it has become quite hard to make a place for yourself. Are you sure that you want to dive into this market? Or are you not taking it too seriously?