First of all, it is not cheating. There are plenty of one-shot collections or reader-request stories on AO3. I personally dislike the practice. It makes tagging useless and the reader often has to sift through a lot of tags they might not like before getting to the ones they want.
I do one shots myself, and while I do generally agree, I try to avoid the major pitfall of having an endless ocean of similar one shots all under one total collection. I tend to view mine as more like an anthology - a loose collection of my short stories, minor works, and ideas that aren't in-depth or expansive enough to warrant a full novel. As such, when my collection gets to about 25-35ish stories, I plan on ending it and starting a new one.
of course, I also plan on publishing them as e-books, so separating them out can make it easier for me to know how big each novel is (chapter-wise).
Yes, but the thing is that I want to post them in one place, not as separate stories.
I refer you to above. It's not cheating to write one-shots. They're basically short stories, which are a LONG recognized story format. Additionally, anthologies are likewise a LONG running publishing thing.
One shots are basically short stories, and One Shot collections are basically anthologies (The central theme would be the author, rather than an abstract idea, like most anthologies). You're not doing anything new and it's certainly not cheating. It's an age old practice. It's always been cheaper to publish one book with fifty short stories than fifty small booklets. That's basically what you're doing.