Got it. As I implied in the OP, how about a more mixed approach... what if Jedis had the array of special abilities that they could use WITHOUT deducting hit points, and ONLY used hit points to recharge or upgrade Force powers in dire straits?
However you implemented it, you'd still have the problem that you were rewarding glass cannon tactics.
Think of it in terms of a game of MtG. We have a fight between two characters who have 20 hit points. To simply, each has a power that says, "Sacrifice X hit points; Do X Damage." MtG actually has a card that works out very close to that. It's called 'Channel'.
How does this fight play out? Well, the first player to gain a life advantage on the other - that is the first person to hit for Y damage - can activate his power to deal X = 20 - Y damage and automaticly win. So the fight comes down to 'who hits first'. This is very much how the Channel+Fireball combo works, except that at least in MtG there were probabilities at play before you could put the combo together (you had to have mana, and channel, and fireball or equivalent, and have a life lead once you did that). Even so, it wasn't very fun in MtG either.
Even if we make the power more balanced like, "Before your attack, sacrifice X hit ponits; If the attach succeeds, do X damage.", the dynamics of the fight don't change much. If you work out the logic, it still ends up being the same swingy fight. If you attack and activate your power, the logic works the same. If you attack and don't activate your power, and miss, then you aren't better off, since you can still lose if your opponent activates his power and hits. If you attack and don't activate your power and hit, you are better off but you are not as well as you would have been had you activated your power (you still haven't won). The only advantageous position to not activate the power is to attack and miss, and then have your opponent attack and miss. But really, this results in a game state exactly the same as the former less balanced power. Since if you don't activate your power, you are gambling that your opponent will miss his attack you are gambling whether you choose to or choose not to activate the powerl; most players will take the active route and gamble on themselves.
In short, it will be very hard to balance this sort of thing. Hit points are a marker of who is winning the battle. Trading hit points for a faster win is just that - faster. But what faster also means in this case is: a) fewer decision points where tactical choices could influence the outcome and b) fewer dice rolls so singular lucky and unlucky rolls are more influential in the outcome.