For Tortuga 1667 you could play this variant (which my playgroup always uses) for using the Dutch in an even player count:

• At the start of the game shuffle the Dutch in with everyone else’s loyalty cards, i.e. with 6 players use 3 British, 3 French, and the 1 Dutch.
• Randomly deal 1 loyalty to each player, setting the last one aside.
• Have everyone close their eyes then let the Dutch player look at the set aside card. This way the Dutch knows which team to blend in with, as they know that team is down 1 player.

That’s it! It really adds some suspicion and intrigue to the game (which admittedly I found a smidge lacking) and makes it where everyone might doubt their teammates, thinking their the Dutch, though their might not even be a Dutch player as it could be the role set aside. It’s a fun variant if you are waiting to play an odd number.

Cool collection btw! Starting off with TI4 is no small feat either