Cubic chunks are different to normal chunks as not all chunks in a column needs to be loaded at once. Also entities are actually part of the chunk instead of the column although in tall worlds entities can also be stored in the column.
The proposed implementation is a hybrid between A column being a whole chunk and being a partial chunk.
There will be control over specific 3d chunks but the ability to reference chunks in 2d that then will load the required sub chunks as needed.
Part of the goal of this fork is to be compatible with MCEdit filters so that migrating them is easy.
All methods that end in _cc will be there for compatibility reasons.
Tall Worlds mod save its chunks to a MapDB database. MapDB is a java library for saving java collections. The file format is complicated so will be hard to implement in python.
So for at least the prototype i have decided to create a java library that reads the data and sends it via socket to mcedit.