I must say I like the game the way it is. However, if _I_ were to change the rules, I think I'd do something about the die immideately after a goal. Perhaps make this an automatic "3" or "4". Rolling "1" or "2" after your opponent scores can prove decicive. Also, rolling a "6" and scoring can turn the tide the other way. I think that of all the die-rolls in the game, the ones directly after a goal are by far the most important.
But, as I said, I like the game as it is. So I try to be prepared for low rolls after an opponent scores, while at the same time being able to score directly if I get a "6".
So, to the proposed changes:
Bigger board: Well, that ensures that one cannot score directly after being scored on, which may be good. But does it make the game more tactical? Assuming we still have the same number of players, it becomes more difficult to play "the whole board" and still be able to make some passes. At least, that's my guess.
Wider goal: Oh, it's MORE than hard enough for the goalie as it is. I think this is a bad idea.
Cards: Probably the biggest change. Not necessarily something negative, but it sure alters the game a lot. I think it might be very interresting, but it's almost an entirely different game.
Only three connected players: I see why you want this, but still think that it's unneccessary. Connected players are strong, but it also have weaknesses, and it cen take some moves to get them positioned like that. I like connecting players.
Standard opening position: Why? If there are optimal starting positions, players will discover them anyway. Also, the best opening position is very different depending on the first die roll (or first card in card version), which is shown BEFORE setup.
80 moves: Probably a good idea with a bigger board and cards. Not a good idea with the current rules.
Offside: I think not. Could cause very weird games, I think.
Diagonal moves: Maybe. Personally, I like the "blocking" effect of two diagonal players, and so prefer it the way it is, but others may feel different.
Attackers/defenders: Like with the cards; this is a major change. Don't combine it with "allow diagonal moves", I think, to make defenders stronger. Can be interresting, but again, a very different game from the existing one.
Three cards in hand: Sure, if cards are used, this may reduce randomness further. I'd probably prefer this if cards were used.
Second half from start position: I think not. Moving into tactical situations, and sacrificing an overall good position to get a temporarily higher scance to score, are to me important aspects. Resetting at half time reduces these aspects.
Multi-player moves. Like with cards, a major change. Interresting, but a very different game.
Summary: I like it the way it is. But new variants are always welcome, as long as the original version stays (original WYPS back, please!). For new variants, one or more of the "major changes" should be effectuated, to make it an entirely new variant, and not just a slight (and possibly annoying) twist to the existing rules.
That's my opinion, anyway! :-)