Hello there,
I am an android developer with grate skills and experience. i have worked on many different apps during my vast experience.
As the code you will get after decompile/reverse engineering is not proper and any developer will not understand it properly so after the code you will not be able to change it easily, even a small change will cost you 3-4 days, and as it is code will make a huge apk file which is also not good for end user, so i think i will be the best option for this task to complete(create new app as you like) smoothly.
lets discuss more about app or any issues/queries you have over a chat.
Hoping for the earliest reply.
Thank you