It's an idea that I had. And I think it deserves to be considered. Especially, such project can assemble people with different views. Emil, for example, cares that this journal can attract scholars with very diverse views on group differences in IQ. As a matter of illustration, I have two books in mind :

Modgil, S., & Modgil, C. (Eds.). (1987). Arthur Jensen: consensus and controversy. Routledge.
Nyborg, H. (Ed.). (2003). The scientific study of general intelligence: tribute to Arthur Jensen. Elsevier.

We can, following what the above authors did, choose one particular topic of discussion, and invite people with different views (the sine qua none condition) to write a chapter (alone or with co-authors). That could be a research article or a commentary. Each person (or group) will submit here a draft version of the chapter. We will read them, make requests if there are any. Each authors can possibly refer to other chapters (this is something they do) in their own discussion.

In some instances, there are books where several authors respond to other authors. This journal can allow that, I think (and I hope).

Of course, one needs to be the editor of the book, and (s)he will write the 1st and last chapter, as well as the introduction section, as is usually the case. The editor of the book should probably decide about the maximum or minimum length of a given chapter. The editor(s) should also be the one(s) to initiate a contact with scholars, describe the main theme of the book, and ask them to write a chapter.

In other journals, the books are not made available. So, OP has a great advantage here. You can capitalize on it.

Now that I think about it, a book should have a cover, with illustration, pictures and colors, and all, no ? Is it necessary ? If so, who is talented enough to perform such a task ?

The more I think about it, the more I'm skeptical. If you want to assemble scholars, that would be near impossible, or it will take at least 10-20 years, if I'm very optimistic. It's bad having to wait that long. So, I was thinking about something else. Something more accessible.

One feature of OP is that it allows pseudonyms. So why not using this at your advantage ? Instead of asking for scholars who only seek celebrity, you can target bloggers. Why not ? It has some originality. A scientific-related book written by non-scholars.

It's even possible to start the project right now.

But in a book, it is usual that we know who the authors are. So, a short presentation is needed, if the author uses a pseudonym; in that case, (s)he should say the blog or website he has, so that we can identify him.

Having lot of HBDers is not a problem for me. I don't think it should be a strict requirement, even though you initially planned to target everyone. But not everyone will join and accept collaborating for a book. Especially anti-HBDers.

Still, someone should decide which subject is worth discussing. If anyone is interested of course.

What are the possible ideas ?

The consequence of IQ in real world...
The possible alternatives to IQ for achieving a high socio-economic outcome...
The questions still unanswered in IQ research, and the possible direction of research...