-Exclude old generic crew for prexisting nations.
Other options:
1) Make single cards that include one of each generic crew for a single nation.
2) Make a few cards of truly *generic* generic crew that can be used on any ship regardless of nationality. Basically, equipment that still counts as crew.
Also, for either of those options instead of printing one of every type of generic crew, you could just print multiples of the ones that are used most often - two or three captains and helmsman, one or two explorers, a navigator, and maybe an oarsman. If someone needs one of the others, they can look to past sets.
There should be no need to print a firepot specialist ever again, unless a completely new nation is created.
The "portrait" cards that WK used, while a great way to show-off nice artwork, were a huge waste of card space. At the very least there should be two named crew per card, but really you could stretch that to four even with one of the smaller standard-sized cards. The tokens, ability text, and point values are the priority. If flavor text won't fit it could always be published online later.
All crew on a card should belong to the same nationality. I frequently pushed for this in the WK sets, and although the designers (Mike/Kelly/etc.) usually agreed, it wasn't always possible given the constraints of the set size.
This is a must. There is absolutely no need to waste precious resources on things that most people have far too much of already, and/or are probably willing to give away for free to anyone that might still need them.
If any UTs are to be included, several should go onto a single card. Four could easily be fit onto a single card, but six would probably be doable too.
Larger ships should definitely be designed around the intent of fitting them onto a single mega card. Multiple (two or three) smaller ships could also be fit onto a single mega card.
The smaller cards in the WK sets were done primarily to keep the booster packs near trading card size, so don't let that be a constraint. Having fewer, but larger cards will mean less to sort out and will greatly reduce the potential for mismatches and other errors.
Easy enough to do, but keep things within reason. Abilities should be printed directly on the cards whenever possible.
Any keyword ability that takes more than a paragraph or two to explain is getting too long. If you create a completely new game mechanic ("sea creatures" for example), try to do as much with general rules as possible, and use those rules on multiple different ships. A long-winded keyword that appears only once in the entire set is a waste of space.
It's also a good idea to avoid arbitrarily creating keywords just to combine multiple existing abilities too. Just because historically a ship might deserve to have the ability to eliminate two masts with a hit, take two hits to lose one of its own masts, ignore terrain, gain +L with all of its masts, and had oars, that doesn't mean you have to squeeze every single one of those into it. Just pick one or two and leave it at that.
Definitely.
Assuming the full/partial set methods are used, a single printed sheet could be included, but the primary source should be online in PDF form. A well-established site like boardgamegeek would be a good place to keep it (or at least a copy of it), so it doesn't vanish forever when the one person hosting it abruptly disappears or simply gets bored and their personal website expires.
Keep the number of different ship types to a minimum, because every new one will require a new cutting die and/or an addition to an existing one. Let people throw out a bunch of different ideas, but then have everyone vote on the "best" four or five to actually put into the set. Once the types are determined, abilities and stats can be adjusted or created around them.
Do not create new nations, unless everyone is willing to see that as the *only* nation in the entire set. Between all of the ones already in the game, the available spaces in the set are already spread pretty thin. Adding more nations that need to be satisfied will only make things worse. As soon as someone starts to complain that a nation got shafted, it's only going to go downhill.