Fernit, From your post it appears that that LAG are hoping for a...

Fernit, From your post it appears that that LAG are hoping for a full blown public hearing, new experts etc, etc. I am taking a rest from @Bowdens at the moment but no doubt another LAGGER will pass this on.

My five cents worth after re-reading the decision .

Yes, this talk of a whole new development application and process is overblown at this stage as no-one know what is going to be in that application.
Yes, the current approval is “void” meaning there is no longer any development consent.
As there is no longer development consent then a new application is required. But information contained in the new application can be substantially the same as the previous application. Except for the inclusion of the 66Kv transmission line, there is no requirement for it to be otherwise. And this is acknowledged in the judgement with reference to the Hoxton Park decision.
As stated at 116 of the judgement, the purpose is to “reopen the development application for further consideration which will require balancing the consideration of such impacts (of the 66Kv transmission line) against other relevant considerations”.
The court of appeal did not make any ruling on how the approval process is administered by consent authority (the IPC) and perhaps this won’t be known until an actual application is lodged. The IPC is unlikely to give any indication prior to that lodgement and an assessment of that document. So the approval process could likely be narrowed to the relevant areas that are impacted on/by the 66Kv transmission line as stated in 116 of judgement.