Details are a bit sketchy and I`m trying to find out more, but something like this...
Horizons was to get a major rehab, somewhere on the scale SSE had in 1994 - all show scenes refreshed, replaced effects, key AAs replaced with A-100s, new lighting and audio systems, updated score, several show scenes post Omnimax replaced, new high res finale films - bascially a good going over of the entire attraction. Before they pulled out, GE had several plans to update and expand their corporate lounge too.
Regarding JIS, version two appears to have been the update of version one, placed between Land and Seas. This version - or a hybrid of it - would possibly have been the one with a centrifuge preshow. There was more to do including several walk through environments as if you were in space, and an updated Omnimax vista from v1. Version 3 would have been in the Horizons show building. Escalators would have taken guests up from the entrance to a new first floor. Directly above this new entrance the Omnimax domes were to have been retained, with stadium seating where the ride path used to be for a new show. The seats would have been motion based - Soarin' wasn`t the first attempt by Disney! Towards the rear of the building would be the obligatory hands on exhibits and a `space colony`, and where the ride system would have been curtailed and retained, offering a `spacewalk` in suspended `spacesuits`.