So I questioned myself why aternos doesn't allow FTP access, and I got an idea for how to make aternos put FTP access.
First for security reasons aternos need to make the users pay 0$ to get their info in case they put a virus jar or a hacking script
In Faq, they need to put the data from the credit card that will not be exposed and it's mainly for security reasons.
The first problem is solved.
The second problem is modifying the jar file and config.
I know it is very hard to make an algorithm to detect a modified jar but it's possible if it tried
The algorithm needs to search on curse forge or other trusted sites, download the file, and inspect it to compare the jar that it has been instaled.
The second problem is solved.
I know this is hard to make because I made an internal server too from scratch, but from hard work from the aternos team, this will be possible, and a lot more users will be happy and more users will come.
Hope this message will get the aternos team's eyes.