Hi.
I am an experienced developer under Google Play Store and I will tell you honestly that 150mb for games created on C3 is a lot.
For example on Unity it is very easy to take this space, it is more bulky.
Maybe your game is a visual novel with lots of high graphics and quality songs. In this case you can load each sprite separately from your site and create a system of levels that will be generated from the array. The array can also be uploaded from the site. But it will require so much effort from you that it will be easier to change the engine.
And most importantly players will not play your game if its size will be more than 30-50mb.