Every wire/tube/whatever you need to be inside the balloon is another place for a seal to fail. If the material of the balloon is transparent to the signal you

Every wire/tube/whatever you need to be inside the balloon is another place for a seal to fail. If the material of the balloon is transparent to the signal you're looking for (as it must be: the reflector is inside and the the universe you want to look at is outside), then there's no benefit to be had.