Hi, there.
With over 8 years of experience as a FullStack Developer, I have worked extensively with the technologies similar to what your project demands. I have built a wide range of scalable and easy-to-maintain applications throughout my career that align perfectly with your APK modification and Firebase integration requirement. During my projects, I always emphasize clean code (MVVM) principles, responsive design, and effective utilization of version control systems - practices which are indispensable in ensuring the highest level of quality software.
In regards to your tool's specific features, I can confidently say that I am more than equipped for the task. Having vast experience with Frontend (HTML/5, CSS/3, JavaScript), Backend (NodeJS, Express), Databases (PostgreSQL, MSSQL, MySQL, Firebase), and even DevOps tools like Azure DevOps Apache,DigitalOcean Amazon AWS;
I've completed numerous projects requiring me to upload files within an interface for further processing – such as your APKs and Firebase configurations requirement. My proficiency with .NET will also be an advantage as it implies that the tool can be desktop-based or web-based based on your preference. Let's discuss your project further so we can develop a top-notch solution that exceeds all your expectations.