Drilled handlebars for aero cable routing used to be somewhat common, and some even came pre-drilled. Like the Mavic bullhorn bars Lemond used in the 89 TdF.

So I have a very similar set of Profile bullhorn "base bars" that I'd like to use without clip ons. Drilling them for internal cables would be the nicest way to do it because it keeps the aero cables aero without running the brake levers upside down.

Pros:
1. It was designed for clip ons, so the tops should be reasonably reinforced for clamping and also for a small oval hole.
2. I can drill a tidy angled hole without any sharp edges or corners.
3. I could epoxy a fiberglass gusset around the hole (but that might just hide a crack from inspection).

Cons:
1. Wasn't designed for drilling per se, and maybe those old bars were thicker or less brittle.
2. I like my teeth.