The end connectors on the Di2/EPS cables would not fit through any cable outer. Unless you cut the wire and re-attached it. Even then you will still struggle to found a cable outer that's wide enough.

Also you will still have a long section of exposed cable for the downtube and chainstay. Seems like a lot of faffing for such small sections of cable.

What's wrong with just a normal external set up ? If its too much exposed cables, then how does adding normal outer make it any better ?

If you do drill the frame. The bottom bracket shell needs to have 3 holes in it also if it hasn't already.