I'm looking to speed up turns and overall gameplay in Starfarers of Catan without reducing victory point milestones. Is it feasible to play the game without event cards if the black ball is given a value of 2? This would reduce emphasis on cannons (and hence, sideline pirate lairs until near the end of the game-probably), but would there be any perceived detriment to gameplay?
You could try it. It probably wouldn't fundamentally ruin the game. It would reduce the randomness. Depending on your group's preferences that could be a good or bad thing. Overall the event cards are more or less breakeven, so removing them wouldn't slow the game down much, and would reduce the reading and decisions encountered in the game, which would probably speed it up.
Normally the black ball sets the base speed to 3 (regardless of what the other ball is); that makes the average base speed 3.5. The second change you propose, to use 2 for the black ball, would raise the average base speed to 4. Not a huge difference and again, unlikely to break the game. And faster movement would get ships to colonizable planets faster.
Cannons would indeed lower in importance, and they're arguably already a lower priority than other uses.