Sure - you can unplug shifters as you see fit. Each shifter has two ports, so you'll have two spare ports to plug other components into. You may be able to fit an SM-JC41 internal Junction B in your quick release aero bars and plug your aero bar shifters into that. Then you would only have to connect the aero bar SM-JC41 whenever to fit the aero bar
Di2 itself does not really care how it is connected, as long as it is. Shimano will recommend you use the EW-JC130 Y-splitter, but you don't have to. Have a look at this video for an alternative:
thanks so much Terry! I did checkout Di2center and whilst there is a heck of a lot of info over there my questions are pretty specific and I couldn’t find the answers nor a forum but I mightn’t have looked hard enough.
for the aero bar setup would there just be a wire coming out of the bar tape that I would connect to the junction box on the aero bar? I can’t quite imagine what it would look like. Wish they would bring out wireless Di2 already even if it still had a central battery so that the cockpit wiring could be eliminated.
I’ll check out the weightweenies link re the front mech - didn’t realise that was a possibility. Does the R8000 Di2 mech result in less tyre clearance than the mechanical version? I’ll check but I don’t think I have a clearance issue now but I don’t know how the di2 version differs.
if I go for it then I’ll go for the GRX rear mech for the reason you mentioned. I read somewhere today that it was more robust.