Georgios, I think I understand your use case, but I'm a little confused by your semantics. You are certainly entitled to your perspective. However, from my perspective GET's constraints are not your only issue. You are not retrieving a resource (the purpose of GET), but rather you are requesting a service which requires an input file. That service transforms the input thereby creating a new resource (the purpose of POST).
The traditional HTTP mechanism for this purpose is multipart form data. The ENCTYPE attribute of <form> tag specifies the method of encoding for the form data. It is one of the two ways of encoding an HTML form. It is specifically used when file uploading is required by an HTML form. It sends the form data to the server in multiple parts because of the potentially large size of the file. This is a normal function of POST.
The Web page gives the user the opportunity to select a local file and the type of transformation desired. The transformed file is returned as the body of the HTTP response — or it can be temporarily or permanently stored on the server and its URL returned in the Location HTTP Header.
This process can be optimized by using file streaming which is available through the JavaScript Streams API on the browser side and through Java (or other) I/O streaming of the server side. As to compression and security, the team I'm on usually uses Zip compression and TLS for communication between requesters and responders.
As to SQL injection, there is a legal term, “attractive nuisance”. If you create one, like an unfenced swimming pool — and then an average person is harmed by using it, you can be liable. In a moral (not legal) sense with software. The average young developer often has neither the training nor the experience to avoid falling for one.
In my 50-years of software engineering perspective, GET's constraints are still valid and QUERY is redundant. Of course, you have every right to your perspective, and it is a pleasure to discuss issues like this with you. That is how our profession makes progress.
