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...I've not seen it done in aluminum, but it's common practice in steel.

With an aluminum BB shell, I'd be more inclined to recommend just installing a sealed BB cartridge unit, and trying to figure out where the water is entering your frame and eliminating those pathways. The seat post/seat tube interface is a logical first stop.

The cons are the obvious greater susceptibility of aluminum to cracks that will form and radiate from the hole in many cases with aluminum tubing. You might be OK in something as heavy and thick as a BB shell, and in fact, I'd not be surprised to see some of them with under the shell routing for the cables. The plastic thingie for the cable routing is often just glued in place, however.