My friends and I love Fireball Island, but not in the way that you're probably used to playing it. Try it with these "enhanced" rules:
1) Draw a card on each white space, instead of each dark space.
2) You can hold up to 10 cards at any given time.
3) You can play as many cards as you want whenever you want.
4) You can play cards in response to other cards: the last card played happens first.
5) If you play a Fireball! card, you MUST honestly try to hit someone with it, even if you're the only one who can get hit by a fireball.
6) You gain control of the jewel whenever you pass the person holding it.
7) Put all the little black hex things on the first turn of the game board and pick one up as you pass it.
8) If you have the little black hex thing, you can only get the jewel stolen by being passed or getting fireballed.
9) You may discard your little black jewel holder to draw 4 cards.
10)First person to the boat with the jewel wins!
11) This rule is important: If you play a "Move back x Spaces" card, you MUST say "Whoa there, (name), not so fast!" to the person you're moving backwards. If you forget to say this phrase, YOU have to move backwards instead. Very important.
Give it a shot!
And I almost forgot--this isn't as much of a rule as it is an enjoyable part of our game.
We lost a hiker, so it has been replaced by a small grey button. When we roll to see who goes first, the person with the lowest score gets the button. They go last, and are mildly taunted for the remainder of the game for getting the button. Even if we have three players, the button must remain in.
If you land on a space with the button, you must put your hiker on top. This is what is known as "surfing the button."
Any Fireball Island story is a good one. Your Mega variant sounds fun.