If you didn't suffer from the presence of a moral code, gene editing babies for intelligence is something you could do today, or if not, with a month or two of preparations and waiting for suppliers.

I would bet that it is possible to expand actual consciousness into connected hardware (silicon or engineered nervous tissue), and have that hardware expand a metric you would call intelligence.

The most reasonable thing in a third direction would be improving brain development through specific training in childhood and training as an adult. A lot of intelligence comes down to how the brain organizes itself in response to inputs, and a scientific discipline to optimize this could make a lot of progress. Not that work isn't being done along these lines but I think there is a lot of room to grow here.