I agree with both of these concepts, both should be something you can do.
I think the Banking Hunger method you proposed is good. And also something that you can probably already do under the rules. If you maneuver/declare that you fed before the fight/during the fight, then you have a Well Fed aspect, and you could of course tag it to boost your Feeding Failure defense roll.
Vampires going all out is also something that should be an option. I think this is best modeled with the temporary powers rules. When a vampire goes all out, they take on a higher level of their Strength/Speed/Toughness/Recovery power (whichever is applicable) temporarily by drawing deeply from their reserves. Then at the end of the scene they face a attack equal to the total refresh of powers they used. This would of course have to cost something (like normal temporary powers), but I think it would be fair to not require the expenditure of a full fate point per refresh of temporary power, since you are paying something by increasing the power of the hunger attack you are going to face later. I am just not sure how much this something is worth. Maybe half a fate point per refresh (so 1 fate point per level per power on Strength/Speed/Toughness/Recovery)? I don't know. It does give you a way to "spend" hunger stress and consequences when you eat that huge attack.
My main problem with spending consequences (and especially stress) to boost a roll is that it feels a bit too much like Sacred Guardian (especially with stress). I know it is somewhat mitigated by the fact that the stress does not clear as normal, but i still think it is too strong. When you only allow consequences it is somewhat better, but still hurt by the fact that you can then go kill a person and clear all your hunger consequences. That may be a somewhat steep cost in some games, but probably less of a cost in others. I just think the potential for a +12 to a roll, and then going and killing something is a bit strong or at least abuseable (if not always strong).
I also feel the problems with Feeding Dependency and the Feeding Powers (Blood Drinker, Emotional Vampire) go further than just not modeling the cases you bring up. I think feeding dependency is extremely unclear in many other ways, and even when you sort through that does not do what I want it to.
I looked over several interpretations/re-writes when I made a White Court character for a game, and here is what I came up with (a lot of credit goes to Becq and Sancta from whom most of these ideas are adapted/copied). I would love feed back on this re-write/houserule of the power (I know Sancta has one that is very general, but I like this more for the types of feeding dependency we see in YS, namely blood and life force via emotions).
Feeding Dependency [+Varies]
Hunger checks are made as in the rules as written (discipline vs refresh used), except that even on a success, a minimum 1-stress hit is inflicted. Stress taken can be reduced as normal by opting to take hunger consequences; the player can also buy down the stress by disabling powers (-1 stress per refresh worth of powers 'lost'). Marking off boxes on the hunger stress track has no additional effect, though the hunger stress track is not automatically cleared as normal at the end of scenes, nor does winning the hunger check clear the stress. Stress that overflows the stress track causes the character to be taken out.
You can feed in order to offset hunger effects. Any time a consequence is inflicted by feeding, any one lesser hunger consequence or any one hunger stress box is cleared. For example, feeding that inflicts a severe consequence allows a mild or moderate hunger consequence, or any one hunger stress box to be cleared. Powers can be recovered in place of a consequence (mild consequence = 2 refresh, moderate = 4 refresh, etc). (If you are allowing partial downgrades, then powers can be partially recovered, too.)
You can also opt out of a scene to feed (you may also feed when there is enough downtime, if you have the night off you may go clubbing and feed as described here, if you have a week off assume you had the opportunity to feed gradually and clear all your problems, subject to GM approval). Describe an appropriate mini-scene and roll an appropriate skill against a difficulty determined by the GM. For example, A WCV that opts out of a scene in order to feed at a rave might test with Presence or Deceit against a mediocre difficulty, whereas a RCV who finds his reserves depleted in the middle of a wilderness might have a much harder time of it. If this check is successful, then shifts can be used to recover powers (one refresh per shift) and/or clear hunger consequences (shift for shift) and/or clear stress boxes (any one box per shift).
Killing while feeding has the same benefit as in RAW: you can immediately regain all of your lost abilities (hunger stress and consequences as well as loss of powers). Note that killing could trigger investigation by police, potentially leading to a conflict (or social consequence involving reputation for being a prime suspect).
Further, since this version adds a more significant gameplay challenge (by requiring “on screen feeding” every so often, or sitting out every few scenes, which is no fun) the rebate should likely be increased. This does depend entirely on how the campaign will be run. If the character is a full White Court Vampire, with no problem with killing, and never faces the consequences of this killing, then [+1] is fine no matter how many powers he puts on it. However, if the character won't kill, can't kill (ie. is a Virgin), or will face severe repercussions from killing (at least some of the time), it may be worth up to [+1] per 2-3 refresh attached.
I suggest [+1] for up to 5 refresh of attached powers, this bonus increases to [+2] at 6 refresh and [+3] at 10 refresh etc.
What do people think?
EDIT: Fixed a particularly egregious spelling error.