Why do you need a mission at all for a large game? Just make it a skirmish and objective is to destroy the opponent's capital ships.
Of task forces, naval squadrons and mighty fleets
Why do you need a mission at all for a large game? Just make it a skirmish and objective is to destroy the opponent's capital ships.
Since very few times are actual battles fought just to kill your opponent. Second to keep pileup near the center of the table from happening. Plus just for flavor and fun since missions deepen the game itself. Though the kill your opponent is fun it does lead itself to certain fleet builds without tons of varity.
If each player takes 3-400 pts and activates one ship each time it's their sides turn it shouldn't bog down too much.
Many years ago some friends and I rented a house in the Blue Mountains and played a huge game, we agreed that we would not take certain weapons and units in order to minimise the scale of the game making the battle one sided. Sad to say the other blokes showed up without miniatures and army lists and therefore took what they had, which just happened to include a large number of weapons and units not to be taken. Now the game was fun, but also quite one sided, we never tried this again.
When playtesting for Flames of War we managed to play their muli-player system and it was a lot of fun. Given a chance we would play that again from time to time. We just ran out of steam having played for about 8-10 years.
As such I think, you want to think about the balance of the game and try to make the multi-player more than just putting two boards together and blowing ships up. Missions are an interesting challenge for players and creates an interesting metagame mechanic as players may not spend the full allotment of points as to play their misions rather than their opponents. You will also need to adjust the table length and width maybe play on a 6x6' or 6x8' table, that will then adjust the turn to play to as the board is much bigger.
If your players don't want to play again, then odds are one side may not have had fun. Both side should have fun and want to play again, so maybe the first few games are "Playtest" games and each player can talk about what they found to be good or bad, then you adjust the rules. Once you have a buy in from the group you have then you can extend the size of the game and introduce more players.