Well, it would be more like $2700 minus sale of my SP3 i7 512. Otherwise I would not consider this at all.Again if you are willing to spend $2,700 on the Surface Book, that amount of money would not get you a "mid-level" gaming desktop. It would be high end, easily.
Hell I would get the i7/16gb/256gb Surface Pro 4 before I would get the $2,700 Surface Book. The SP4 i7 comes with the Iris Graphics and at this point I don't think there is going to be much of a difference between that and the GPU in the Book. Close to $1,000 cheaper for very similar performance.
If the form factor of the SB is not the be-all-end-all deciding factor for you, then I see very little reason to buy it. You could get much more power for cheaper.
Form factor not so much a selling point and I have no issues with the SP3 keyboard. But if the dGPU vs SP4 GPU is not that different, then that would be a sticking point.