So, a double-post, but I think it's about time I gave a clear verdict one way or another regarding this behaviour:
In its current state (and considering my current circumstances) it's safe to say that I'm unable to continue developing this.
I haven't wanted to outright say "no I'm not working on this anymore" because the longer I went without updating this the worse it would look and I'd hoped to make at least SOME progress, but it's been so long that I think the lack of progress has given enough of an indication of disinterest, so I might as well make sure it's clear rather than just implied.
To lay out a few of the issues and give a general indication of why:
Between the messy code and my inability to commit time to this, it became difficult to make any proper headway at all, since most development was in very isolated chunks. As time has passed it's only made it harder to look at the code and not simply see a demotivating brick wall.
I've made a couple attempts here and there to sit down and finish a couple of the bigger bits on the todo list (tilemaps, basically) and between either a lack of skill/understanding on my part or me simply trying to twist bits of C2 that weren't quite intended to be used for this particular thing (or at least not in the way I'm trying to do it) it just keeps falling apart. So I'm afraid I don't have a nice final clean "no-longer-blatantly-unfinished" update.
So yeah, it was still a fun little project, and I've been pleasantly surprised to see how much use people have squeezed out of it. Maybe I'll have a go at a more reasonably-scoped project in the future, see if I can make something a little more complete.
Thanks again for the feedback/interaction.