"Fatigue"-based Magic System Thoughts

Hey there everyone! Not very active here, am I? Well, such is life, but it doesn't mean that I don't still have ideas racing around in my head on this little project.  I still intend to do a "straight" cyberpunk ruleset as the initial phase of CHROME, but the fantasy bits will come, and the idea for a way to handle spell casting has more or less come together in my head over the last couple of days.  The rambling essay below is more to get it on paper than anything else. Thoughts and feedback are certainly welcomed.

Ok, so I've got this idea for a more free-form magic system than the "stock" D&D version. I might well be right off my rocker on this. It's inspired by a few things - the idea of a spell point system rather than strict Vancian memorization, the S&W/Akratic Wizardry magic house rules where spells burn hit points as a measure of fatigue, and an optional bit tagged on the end that harkens back to Shadowrun's dice pool & spell fatigue concepts. Kind of. I want a more 3E sorcerer feel to magic - a limit on available spells, but more freedom to cast them at will. 

MUs gain a pool of spell points equal to their level, and spells cost one SP per level to cast. Casting will first use the points drawn from this pool - an arcane "battery" if you will, that represents them being stronger in magic as they increase in level. You'll note however, that a third level MU has just 3 points - that's just 3 first level spells, or one first and one second, compared to 3 first and 1 second under the standard system. So, on top of these spell points, the MU can continue to cast spells by burning HP instead of designated SP. This method assumes you look at hit points in the abstract sense of being a measure of luck, fatigue, nicks & scraps rather than real damage. As you use up HP, you become more fatigued, finally falling unconscious at 0. In my games, death doesn't occur at zero, but rather at -HP equal to level + CON bonus, representative of "real" damage below zero.

Since MUs have relatively low HP this doesn't seem too overpowered to me, but allows them the option of casting more spells per day if they are willing to pay the price. If they end up in more combat later on, they are already down on HP and easier to kill.

Casters still use the MU spells memorized table for the spells in their head, available to cast at any given time, and they can change what they have memorized after a nights rest. I'm thinking they also can have a number of additional spells memorized equal to their INT modifier, that can be used for any level of spells they are able to cast. So, a third level MU with a 17 INT would memorize 3 first level and 1 second level spell, plus two more of either level, for a total load-out of six spells available to cast.

The last piece of the puzzle is the idea of a dice pool as a further power balancing mechanic. Since I've allowed them to memorize more spells than normal, there should be a chance to lose those as well - a skill check sort of thing. After casting a spell, the MU rolls a number of d6 equal to his level. If he rolls at least one 6, then the spell is cast, SP (or HP) burned and he retains the spell in memory to be cast again. If the roll comes up ALL 6s, it's a critical success and the spell goes off WITHOUT using up any spell points. Conversely, if the roll comes up all ONES, it's a critical failure and while the spell is cast successfully, it is lost from memory until re-memorized the next day. I'm iffy on this part - not sure if the spell should fail as well on a critical failure.