The current Developer class approach is just not satisfying enough. There are some loose ends to be cleaned up and is difficult to achieve with current structure (e.g. no prevents to client-side crash for developer blocks).

I think it is approprate to take the advantage that ANY developer can and can only be used by one player. We can store develop progress information in a DataPart, and reroute item energy handler/ tile entity into that DataPart when develop process begins.

Some of the work done via 0d8a593.
However it is clear that this part of code is in bad health... Many workarounds and bad code placements.
Consider sorting the GUI stuff up.

This is finished and shall be closed. Next time consider stashing the commits XD