Yes, it has inputs/outputs for MIDI, audio etc. These are placed on the back; which I prefer, for all the cables remain out of sight (assuming you will place the instrument up against the wall).
If the instrument is in good condition, go for it ($2,000). Pairing it with Pianoteq will give you much better results than buying any of the newer offerings from the big three.
A real action is not a gimmick. No folded action can come close to it, and in terms of Kawai's pivot-based action, no , that does not come close to a real upright action neither.
I don't believe that the extra sensor on the GF (Kawai) action will give you any true advantage in terms of repetition over the GT's action.
Honestly, I've not noticed much improvement over two-sensor actions. Like counting layers in a sampled piano, more sensors gives an immediate impression of being better, "the more the better;" however, that is not always the case. Yes, the experts will tell you why a third sensor improves repetition from a theoretical perspective, but as we all know, a lot can happen between theory to implementation. My self-cleaning oven can theoretically clean itself, yet if I don't go in there myself, there always remains a bit of last thanksgiving's turkey (I'm being facetious; I can't even cook, but you get the point).