With not only STJr's free time running out, but also the fact that it difficult to edit SRB2(not to mention there is no profit involved, and the general lack of motivation), I have thought about something: Does Dark City Zone really need to be made? Not only is it almost completely devoid of proper textures(current ones apparently are dated), but what would it offer that Egg Rock doesn't? From the sound of it, it probably would be a hazardous, grim looking city stage with a bunch of pits and the like. Unless the dev team has some really good ideas for it, it just looks like an inferior Egg Rock on paper. Don't forgot that many players have already played and completed Egg Rock, so if Dark City doesn't offer much unique, it will feel a bit like a step down from ERZ. And Black Eggman doesn't really need to be in DCZ(though it is true that he was designed as that stage's boss); he seems to fit in fine with ERZ(the "buildings" can just become platforms).
While I'm at it, I'll list the stages that don't exist yet:
CEZ3
ACZ2-3
RVZ/BMZ(?)2-3
DCZ1-2
Real ERZ3
FFZ
That's nine acts missing; five of them being bosses(including the possible Metal Sonic boss, which I can't imagine being the sole boss of ERZ3, unless FFZ isn't a Super Sonic stage), 3 of them somewhat being DCZ. Take out DCZ(as well as place BE elsewhere), and you pretty much only have ACZ2 and RVZ/BMZ(?)2 left as the only nonexistent non-boss acts. Of course, there is still unfinished maps like CEZ1-2 and RVZ1.
On another subject, what is the deal with Blue Mountain Zone anyway? Supposedly, it was simply a proof-of-concept map that got left in 2.0 when it was released. However, BMZ actually sounds like it would be a better idea than RVZ2. I can't think of much that would set RVZ2 apart from RVZ1(then again, Lava Reef Zone managed to pull it off). BMZ however would not only would likely have more unique gimmicks, it also has a ton of textures to work with. Plus, the fact that Egg Rock itself is littered with lava somewhat makes RVZ2 a bit redundant.
Of course, at the end, if STJr is able to pull off DCZ well, I'm all in for it. Though to be fair, seven zones seems to be a good number for SRB2. If it doesn't seem like DCZ could be made unique though(let alone have the time to make the textures for it), it would be better to focus on the other zones first. After all, as stated in the beginning of this post and throughout the topic, STJr is running out of free time and motivation. A simple difficulty increase for the zones before ERZ can probably help smooth out the difficulty curve if there is no time to make DCZ.