Now that I spent some thinking on how to make initial setups cannon-proof, I started worrying about Gigachess. The 4 central files her contain a stack of valuable pieces, which could easily be skewered by the much less valuable Cannon. So a good opening plan seems to be 1. Ec4 ... 2. a5 ... 3. a7 ... 4. Ca5, after which the Cannon has the choice between f5, g5, h5 and i5. This takes only 5 moves, and it will be hard for black to rescue all four central files, by blocking the Cannon's attack with an extra piece, or evacuating them. In fact it is quite hard to get any pieces there at all: it takes two moves to get a Knight to the f- or i-file, while the g- and h-file can only be reached by a Prince in two moves.
Of course when two Knights or Princes can reach these ranks, they could defend against the Cannon attack 'dynamically', by following the Cannon each time it redirects its attack to a new file. But that would still be an easy way for white to force a draw by repetition.
Now that I spent some thinking on how to make initial setups cannon-proof, I started worrying about Gigachess. The 4 central files her contain a stack of valuable pieces, which could easily be skewered by the much less valuable Cannon. So a good opening plan seems to be 1. Ec4 ... 2. a5 ... 3. a7 ... 4. Ca5, after which the Cannon has the choice between f5, g5, h5 and i5. This takes only 5 moves, and it will be hard for black to rescue all four central files, by blocking the Cannon's attack with an extra piece, or evacuating them. In fact it is quite hard to get any pieces there at all: it takes two moves to get a Knight to the f- or i-file, while the g- and h-file can only be reached by a Prince in two moves.
Of course when two Knights or Princes can reach these ranks, they could defend against the Cannon attack 'dynamically', by following the Cannon each time it redirects its attack to a new file. But that would still be an easy way for white to force a draw by repetition.