di2 build with complications

 I need advise on  a project I have, my dedline for when the project starts is newyears. I have a trek 2100zr. If your not fimiliar with it, it is an aluminum bike with carbon seat stays and fork. I intend to replace its mix of 9, 10, and even 11 speed mismatched components, with dura ace 9070 groupset(Ive opted for 9070 insted of 9150 for astedic reasons). I want to use the internal battery instead of the external batter. but my bike has no internal cable routing, since I already bought the parts I am just going to make it work. I have no fear of voiding the warenty, because ive already doen that after getting a braze on mount welded on to the frame because at the time I was  unawear that there was an adapter. I am not afraid to dril the frame, I know a guy who works at a machine shop and is willing to help me drill the holes. I want to finde a method that hides the cables fairly wel and puts the battery in the frame and uses my jc41 junction, because I am not interested in buying a jc40.I can 3d print simple parts to alow me to achive this goal. 

reguirements:

I need full drive train functionality

battery to be mounted internaly

I cant buy any new components because my money is wrped up in raxce entrys for 2020

no holes in the carbon seat stays

no modification to the components other than heatshrink

it NEEDS to be water proof because I ride in the rain alot

goals:

minimal holes

clean look

aero

I would prefer to avoid removing the bb(rather drill an extra hole that remove the bb, unles it means no holes in my frame)

ive thouht about puting the junction b on my chai stay and routing the di2 cable throught that hole in my chain stay to the battery, If that will work, that would be my prefered option,

thanks in advance for any help that I can get!