What I would do (and I acknowledge that this is very personal) would be to string the cables for the electronic group set externally where the steel cables for the mechanical group set go.
Run the electronic cable in sheath from the bars to the downtube termination points, then run it under tension (maybe heat shrink it to a steel cable?) to the BB and then onto the relevant mech.
That way you retain the look, it’s a nice technical challenge (very easy for it to look bad, you’ll have to work at it for it to look neat) and if you put enough work into it you will make everyone who knows what they’re looking at do a huge double take.
What I would do (and I acknowledge that this is very personal) would be to string the cables for the electronic group set externally where the steel cables for the mechanical group set go.
Run the electronic cable in sheath from the bars to the downtube termination points, then run it under tension (maybe heat shrink it to a steel cable?) to the BB and then onto the relevant mech.
That way you retain the look, it’s a nice technical challenge (very easy for it to look bad, you’ll have to work at it for it to look neat) and if you put enough work into it you will make everyone who knows what they’re looking at do a huge double take.