I havn't really had a comment on this argument until recently, where it has been my painful pleasure to come up against multiple opponents with nova cannon fleets. The ability to start the game bombarding you with potentially crippling shots in your own DZ was quite a reminder of the NC power.
I found that this was especially effective against large base ships.
This becomes even more dramatic once you enter the 2d6 and 1d6 band.
Scattering 1d6 on a large base is almost as good as a direct hit, and due to some below average BFI dice, my Battleship and Grand Cruiser
were both crippled by nova cannons before they could close to 30cm, along with a cumulative 5 hits on my cruisers. This was with below than 33%
hit ratio.
I really love the idea of the IN torpedo wall, but multiple novas have been proven to be more effective, at least against my Chaos fleet.
Actually improving the nova is ludicrous.
I propose no limit, but the innacurate weapons always scatter 3d6.