A: Doubling the playing deck should not cause any issues, but for more people, you’re proposing doubling the number of Goals, which we would not generally suggest, as it raises awkward issues, some of which you have considered. It sounds like you’ve worked out some proposed ways to handle some of these yourself. (You’ve suggested that two players are going for the same Goal then the one that makes the winning play is the one that gets the win – that’s a decent solution). If you consider and work out rulings for possible complications, there’s no reason you couldn’t give it a try.
Besides potential conflicts, which could be worked out, however, we have a few more caveats. You may find that it gets to be a long time between turns if more than five are playing. Also, if there is a double of one Goal (actually in play), but not others, those two players will find themselves with what may seem like an unfair advantage. We’d also recommend that you keep the unused Goals in a specific ordered chain outside of the game (which we advise in the regular game as well), so that the Rotate Goals Action can be used to bring those in and out of play in a static order, and not just randomly. You could even insert the unused Goals in between players so that the unused chain of Goals is not so long.
To make a long story short: we don’t recommend it, for various reasons, so we don’t have a lot of guidlines for people. So just experiment with it. You may find you need to develop some other house rules… or you may find that it’s not as fun as simply breaking into two games. But give it a try!
Note that if you need to separate two decks again, we have a handy card list of sorts, to help you get them all distributed right:
if you have the first edition (square Goal images, no diagonals) here is the card list: