Is it possible to create an online service that allows you to make graphical changes based on layers?

Question

Computer networks

Good day !
I appeal to everyone who knows for help in finding an answer to a question that torments me. The next task is to simplify as much as possible the work of a designer in a remote mode, to the maximum possible level, on the development of banner advertising in different sizes.
1. We came to the conclusion that you need to make an online service like avatan.ru or picnik-photoshop.ru they have everything, but there are a few details that kill this idea. The bottom line is that these services do not save layers during operation, therefore, when saving each operation, we have a JPG, and when edits occur, such a format, as you know, cannot be edited. The second trouble is that even if there are layers, the PSD format is still not available for them.
Question No. 1 Is it possible to make an online service that could support layering, with a number of primitive functions?
Question to those who know No. 2 Here is a service similar to www.photopea.com , how difficult is it to make?
Question number 3 Maybe there is already a similar open source editor that can be "finished" to your own needs?
Question No. 4 Assuming that a similar service already exists, do you think it is possible to reload, for example, text, directly into the program according to a previously known template?
2. If it is very problematic and costly to create such a service, then another question arises, is it possible to create a certain template "semi-finished product" created automatically "programmatically" based on the technical specifications for the banner immediately in the format ?
Interested specifically in text fragments in known places + certain PNG fragments.
I earnestly ask you not to "hit" strongly if I ask something wrong somewhere, I ask you to answer on the specifics of the questions. Any comments or suggestions will be welcomed and taken into account.
Thank you for your responses.

Answer 1

It all comes down to time and money. Everything can be done. I don't know open source.
But I can help with the server part so that everything is fast.
If there is something to pay, then welcome.