Nice bike!
I'm similar to you in that I have one bike, my arkose 3 which has seen me upgrade the brakes to hydraulics, and the wheels to Hunt Gravel. The last payment comes out for it this month and it will all be paid off. Like you I wanted a "do it all bike" but I find myself more and more on road and I fancy an N+1. Thinking something a bit road racier. Currently looking at Trek Emonda ALR5 with budget left to buy a nice wheel upgrade. Or perhaps a CAAD12 105 or SuperSix Evo 105, bit more so wheel upgrade budget will be less or have to wait.
Thinking of popping to the
Evans in Gatwick to try them out for size tomorrow as not working, looking at the geometry the Trek is the nearest to my Arkose while the two Cannondales are a bit more agressive.
Di2 is well beyond my budget really, but your Giant does look nice. Enjoy!