Okay, postmortem time! I kinda did one in video form on Sunday, but I might as well summarize it here.
Basically, I took on too much given my fairly slow mapping pace, coupled with this being a busy month IRL for me (family wedding, friends visiting, doing some home furnishings, etc.). Even so, I ended up with one map that's practically complete, barring population (still working on that one!) and a complete shell that I'm currently working on texturing. That, plus a gameplay mod that shows promise. That's still noticeably faster than I'd ever mapped anything, so I guess I'm learning to be more efficient, or something.
I knew I wasn't going to be able to "complete" this project, but I was hoping that I'd have a bit more to show for it. Even so, that's two maps that I didn't have on the 30th of September! I plan to continue to develop this, as well as show off my progress in regular video updates (a playlist—including four weekly updates from this month—can be found here, for those interested in following along). I feel that the concept shows promise, at least, and I do plan to release the resource pack separately for anyone who wants to design maps around it. Might be kind of a niche thing, but it'll be there if anyone wants it. :)
The main takeaway for me is that I should have started with a simpler project, given that I'm new to time-constrained projects. Maybe a single larger map or trio of smaller, less ambitious maps for starters. Designing a series with three distinct parts, coupled with a gameplay mod, is a bit…ambitious. The gameplay mod proved to be a bit of a misstep. I mistakenly believed that it was Good Enough™ and would only need minimal polish and maybe a few bestiary additions, but that proved to be wildly inaccurate. Speaking of which, I'd like to give a huge thanks to @Scypek2 for planting the seed in my mind that perhaps my initial ballistic weapons were a bit too samey.
So, I think that's it for now. I'm going to take a few days to relax and try to catch up on my usual upload schedule. After that, I think I might dive back into the gameplay mod. I still need to come up with a BFG replacement, after all.