At this point, if they were reasonable developers, they would simply stop updating the game. Keep the same pace of releases of only the pictures in the picture packs we already get, and start work right away on remaking the game on a proper game engine that works. As soon as you have something that works, perhaps on the same open-source engine as Summertime Saga, start implementing the new characters in that first. Get to the older characters later.
Emphasis on the if.
Honestly, as much I hate to suggest they go about it this way, I think they should fix up what they have then start fresh on a 'Season 2' version, seeing as the WW cell scenes should wrap up the original lineup's content. This way they can move the story forward without having all that pesky previous content just getting in the way and breaking itself. I'm typical not a fan of when games do this, but in this case it would fit the setting and, fingers crossed, maybe the time used to fix bugs can then be put towards learning how to Unity and optimize the game a smidge (let's face it, the fact this game takes 10 gigs of space is a bit much).
On the other hand, since I previously alluded to the fact I'm just about more interested in the bugs than actual updated story at this point, I'm perfectly fine either way.
"We will be sure to have it out before the end of the month."
Radio fucking silence.
Seeing as the alternative is a daily update which effectively amounts to this:
I could understand why one would choose silence. (Then again, I'm just using this as an excuse to post that gif, as I find it applies to many parts of this thread as well.)