I'm gonna play devil's advocate here for a moment.
The purpose of a dev thread isn't, or at least shouldn't, be to discourage people from posting submissions with unusual properties or that may be overpowered. There's always the temptation to slap someone with dev because you know they'll give you trouble if you outright deny them or demand changes. After all, they wouldn't be submitting their 10 level armor made from six inches of beskar and unicorn poo if they weren't trying to avoid work in the first place. However, that's not what they're there for.
Ideally, a dev thread should be an opportunity. The FJ is acknowledging that the project deserves some extra attention, and rather than arbitrarily nerfing parts of it, they're giving the submitter a chance to work for their stuff. That, I think, is a critical part of the Factory.
If you nix dev threads altogether, outside of the aforementioned restricted materials and what have you, you will simplify the process. There's no denying that. But you also take away that tool that allows more ambitious or creative writers to push boundaries and come up with something awesome.
I get the whole "well the FJ can just nerf it or deny it instead" thing, but I think that's the wrong answer. Each FJ and CJ looks at things a little differently. Each one has their own views and experiences that color the way they handle submissions. Some know ships inside and out, and some know armor. That diversity of thought is important, but it makes it hard to have a standard for what is and isn't OP. I once had a project where one judge demanded several arbitrary changes that would have completely defeated the point of the thing. I second chanced and the next judge was fine with it. The first judge didn't do anything wrong, they simply didn't have the frame of reference needed to get what was going on.
I suspect that, without dev threads, you'll see a lot more cases like that. This, in turn, will increase the workload of the Factory staff, which rather defeats the purpose.
Perhaps you could make the dev threads an option, to be used at the judge's discretion. That's what I usually tried to do as a judge, and it seemed to work. You tend to get a lot less pushback if people have options, rather than just making demands.