Other than the saddle and post it looks perfect. Just fix what's broken and then hammer fuck out of it. If the gears are fucked I'd probably SS it before bothering with any new shifty stuff.
So, now OP needs to find something else to build. Can you make me a complete functional copy of a Bullitt cargo bike? I'll give you 48 pesos when it's complete.
Other than the saddle and post it looks perfect. Just fix what's broken and then hammer fuck out of it. If the gears are fucked I'd probably SS it before bothering with any new shifty stuff.